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12.5: The Language of Epidemiologists - Biology

12.5: The Language of Epidemiologists - Biology


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Learning Objectives

  • Explain the difference between prevalence and incidence of disease
  • Distinguish the characteristics of sporadic, endemic, epidemic, and pandemic diseases
  • Explain the use of Koch’s postulates and their modifications to determine the etiology of disease
  • Summarize Koch’s postulates and molecular Koch’s postulates, respectively, and explain their significance and limitations
  • Explain the relationship between epidemiology and public health
  • Describe the entities involved in international public health and their activities
  • Identify and differentiate between emerging and reemerging infectious diseases

The field of epidemiology concerns the geographical distribution and timing of infectious disease occurrences and how they are transmitted and maintained in nature, with the goal of recognizing and controlling outbreaks. The science of epidemiology includes etiology (the study of the causes of disease) and investigation of disease transmission (mechanisms by which a disease is spread).

Analyzing Disease in a Population

Epidemiological analyses are always carried out with reference to a population, which is the group of individuals that are at risk for the disease or condition. The population can be defined geographically, but if only a portion of the individuals in that area are susceptible, additional criteria may be required. Susceptible individuals may be defined by particular behaviors, such as intravenous drug use, owning particular pets, or membership in an institution, such as a college. Being able to define the population is important because most measures of interest in epidemiology are made with reference to the size of the population.

The state of being diseased is called morbidity. Morbidity in a population can be expressed in a few different ways. Morbidity or total morbidity is expressed in numbers of individuals without reference to the size of the population. The morbidity rate can be expressed as the number of diseased individuals out of a standard number of individuals in the population, such as 100,000, or as a percent of the population.

There are two aspects of morbidity that are relevant to an epidemiologist: a disease’s prevalence and its incidence. Prevalence is the number, or proportion, of individuals with a particular illness in a given population at a point in time. For example, the Centers for Disease Control and Prevention (CDC) estimated that in 2012, there were about 1.2 million people 13 years and older with an active human immunodeficiency virus (HIV) infection. Expressed as a proportion, or rate, this is a prevalence of 467 infected persons per 100,000 in the population.1 On the other hand, incidence is the number or proportion of new cases in a period of time. For the same year and population, the CDC estimates that there were 43,165 newly diagnosed cases of HIV infection, which is an incidence of 13.7 new cases per 100,000 in the population.2 The relationship between incidence and prevalence can be seen in Figure (PageIndex{1}). For a chronic disease like HIV infection, prevalence will generally be higher than incidence because it represents the cumulative number of new cases over many years minus the number of cases that are no longer active (e.g., because the patient died or was cured).

In addition to morbidity rates, the incidence and prevalence of mortality (death) may also be reported. A mortality rate can be expressed as the percentage of the population that has died from a disease or as the number of deaths per 100,000 persons (or other suitable standard number).

Exercise (PageIndex{1})

  1. Explain the difference between incidence and prevalence.
  2. Describe how morbidity and mortality rates are expressed.

Patterns of Incidence

Diseases that are seen only occasionally, and usually without geographic concentration, are called sporadic diseases. Examples of sporadic diseases include tetanus, rabies, and plague. In the United States, Clostridium tetani, the bacterium that causes tetanus, is ubiquitous in the soil environment, but incidences of infection occur only rarely and in scattered locations because most individuals are vaccinated, clean wounds appropriately, or are only rarely in a situation that would cause infection.3 Likewise in the United States there are a few scattered cases of plague each year, usually contracted from rodents in rural areas in the western states.4

Diseases that are constantly present (often at a low level) in a population within a particular geographic region are called endemic diseases. For example, malaria is endemic to some regions of Brazil, but is not endemic to the United States.

Diseases for which a larger than expected number of cases occurs in a short time within a geographic region are called epidemic diseases. Influenza is a good example of a commonly epidemic disease. Incidence patterns of influenza tend to rise each winter in the northern hemisphere. These seasonal increases are expected, so it would not be accurate to say that influenza is epidemic every winter; however, some winters have an usually large number of seasonal influenza cases in particular regions, and such situations would qualify as epidemics (Figure (PageIndex{2}) and Figure (PageIndex{3})).

An epidemic disease signals the breakdown of an equilibrium in disease frequency, often resulting from some change in environmental conditions or in the population. In the case of influenza, the disruption can be due to antigenic shift or drift, which allows influenza virus strains to circumvent the acquired immunity of their human hosts.

An epidemic that occurs on a worldwide scale is called a pandemic disease. For example, HIV/AIDS is a pandemic disease and novel influenza virus strains often become pandemic.

Exercise (PageIndex{2})

  1. Explain the difference between sporadic and endemic disease.
  2. Explain the difference between endemic and epidemic disease.

Etiology

When studying an epidemic, an epidemiologist’s first task is to determinate the cause of the disease, called the etiologic agent or causative agent. Connecting a disease to a specific pathogen can be challenging because of the extra effort typically required to demonstrate direct causation as opposed to a simple association. It is not enough to observe an association between a disease and a suspected pathogen; controlled experiments are needed to eliminate other possible causes. In addition, pathogens are typically difficult to detect when there is no immediate clue as to what is causing the outbreak. Signs and symptoms of disease are also commonly nonspecific, meaning that many different agents can give rise to the same set of signs and symptoms. This complicates diagnosis even when a causative agent is familiar to scientists.

Robert Koch was the first scientist to specifically demonstrate the causative agent of a disease (anthrax) in the late 1800s. Koch developed four criteria, now known as Koch’s postulates, which had to be met in order to positively link a disease with a pathogenic microbe. Without Koch’s postulates, the Golden Age of Microbiology would not have occurred. Between 1876 and 1905, many common diseases were linked with their etiologic agents, including cholera, diphtheria, gonorrhea, meningitis, plague, syphilis, tetanus, and tuberculosis. Today, we use the molecular Koch’s postulates, a variation of Koch’s original postulates that can be used to establish a link between the disease state and virulence traits unique to a pathogenic strain of a microbe.

Koch’s Postulates

In 1884, Koch published four postulates that summarized his method for determining whether a particular microorganism was the cause of a particular disease. Each of Koch’s postulates represents a criterion that must be met before a disease can be positively linked with a pathogen. In order to determine whether the criteria are met, tests are performed on laboratory animals and cultures from healthy and diseased animals are compared (Figure (PageIndex{4})).

Koch’s Postulates

  1. The suspected pathogen must be found in every case of disease and not be found in healthy individuals.
  2. The suspected pathogen can be isolated and grown in pure culture.
  3. A healthy test subject infected with the suspected pathogen must develop the same signs and symptoms of disease as seen in postulate
  4. The pathogen must be re-isolated from the new host and must be identical to the pathogen from postulate 2.

In many ways, Koch’s postulates are still central to our current understanding of the causes of disease. However, advances in microbiology have revealed some important limitations in Koch’s criteria. Koch made several assumptions that we now know are untrue in many cases. The first relates to postulate 1, which assumes that pathogens are only found in diseased, not healthy, individuals. This is not true for many pathogens. For example, H. pylori, described earlier in this chapter as a pathogen causing chronic gastritis, is also part of the normal microbiota of the stomach in many healthy humans who never develop gastritis. It is estimated that upwards of 50% of the human population acquires H. pylori early in life, with most maintaining it as part of the normal microbiota for the rest of their life without ever developing disease.

Koch’s second faulty assumption was that all healthy test subjects are equally susceptible to disease. We now know that individuals are not equally susceptible to disease. Individuals are unique in terms of their microbiota and the state of their immune system at any given time. The makeup of the resident microbiota can influence an individual’s susceptibility to an infection. Members of the normal microbiota play an important role in immunity by inhibiting the growth of transient pathogens. In some cases, the microbiota may prevent a pathogen from establishing an infection; in others, it may not prevent an infection altogether but may influence the severity or type of signs and symptoms. As a result, two individuals with the same disease may not always present with the same signs and symptoms. In addition, some individuals have stronger immune systems than others. Individuals with immune systems weakened by age or an unrelated illness are much more susceptible to certain infections than individuals with strong immune systems.

Koch also assumed that all pathogens are microorganisms that can be grown in pure culture (postulate 2) and that animals could serve as reliable models for human disease. However, we now know that not all pathogens can be grown in pure culture, and many human diseases cannot be reliably replicated in animal hosts. Viruses and certain bacteria, including Rickettsia and Chlamydia, are obligate intracellular pathogens that can grow only when inside a host cell. If a microbe cannot be cultured, a researcher cannot move past postulate 2. Likewise, without a suitable nonhuman host, a researcher cannot evaluate postulate 2 without deliberately infecting humans, which presents obvious ethical concerns. AIDS is an example of such a disease because the human immunodeficiency virus (HIV) only causes disease in humans.

Exercise (PageIndex{3})

Briefly summarize the limitations of Koch’s postulates.

Molecular Koch’s Postulates

In 1988, Stanley Falkow (1934–) proposed a revised form of Koch’s postulates known as molecular Koch’s postulates. These are listed in the left column of Table (PageIndex{1}). The premise for molecular Koch’s postulates is not in the ability to isolate a particular pathogen but rather to identify a gene that may cause the organism to be pathogenic.

Falkow’s modifications to Koch’s original postulates explain not only infections caused by intracellular pathogens but also the existence of pathogenic strains of organisms that are usually nonpathogenic. For example, the predominant form of the bacterium Escherichia coli is a member of the normal microbiota of the human intestine and is generally considered harmless. However, there are pathogenic strains of E. coli such as enterotoxigenic E. coli (ETEC) and enterohemorrhagic E. coli (O157:H7) (EHEC). We now know ETEC and EHEC exist because of the acquisition of new genes by the once-harmless E. coli, which, in the form of these pathogenic strains, is now capable of producing toxins and causing illness. The pathogenic forms resulted from minor genetic changes. The right-side column of Table (PageIndex{1}) illustrates how molecular Koch’s postulates can be applied to identify EHEC as a pathogenic bacterium.

Table (PageIndex{1}): Molecular Koch’s Postulates Applied to EHEC
Molecular Koch’s PostulatesApplication to EHEC
(1) The phenotype (sign or symptom of disease) should be associated only with pathogenic strains of a species.EHEC causes intestinal inflammation and diarrhea, whereas nonpathogenic strains of E. coli do not.
(2) Inactivation of the suspected gene(s) associated with pathogenicity should result in a measurable loss of pathogenicity.One of the genes in EHEC encodes for Shiga toxin, a bacterial toxin (poison) that inhibits protein synthesis. Inactivating this gene reduces the bacteria’s ability to cause disease.
(3) Reversion of the inactive gene should restore the disease phenotype.By adding the gene that encodes the toxin back into the genome (e.g., with a phage or plasmid), EHEC’s ability to cause disease is restored.

As with Koch’s original postulates, the molecular Koch’s postulates have limitations. For example, genetic manipulation of some pathogens is not possible using current methods of molecular genetics. In a similar vein, some diseases do not have suitable animal models, which limits the utility of both the original and molecular postulates.

Exercise (PageIndex{4})

  • Explain the differences between Koch’s original postulates and the molecular Koch’s postulates.
  • List some challenges to determining the causative agent of a disease outbreak.

The Role of Public Health Organizations

The main national public health agency in the United States is the Centers for Disease Control and Prevention (CDC), an agency of the Department of Health and Human Services. The CDC is charged with protecting the public from disease and injury. One way that the CDC carries out this mission is by overseeing the National Notifiable Disease Surveillance System (NNDSS) in cooperation with regional, state, and territorial public health departments. The NNDSS monitors diseases considered to be of public health importance on a national scale. Such diseases are called notifiable diseases or reportable diseases because all cases must be reported to the CDC. A physician treating a patient with a notifiable disease is legally required to submit a report on the case. Notifiable diseases include HIV infection, measles, West Nile virus infections, and many others. Some states have their own lists of notifiable diseases that include diseases beyond those on the CDC’s list.

Notifiable diseases are tracked by epidemiological studies and the data is used to inform health-care providers and the public about possible risks. The CDC publishes the Morbidity and Mortality Weekly Report (MMWR), which provides physicians and health-care workers with updates on public health issues and the latest data pertaining to notifiable diseases. Table (PageIndex{2}) is an example of the kind of data contained in the MMWR.

Table (PageIndex{2}): Incidence of Four Notifiable Diseases in the United States, Week Ending January 2, 2016

DiseaseCurrent Week (Jan 2, 2016)Median of Previous 52 WeeksMaximum of Previous 52 WeeksCumulative Cases 2015
Campylobacteriosis4068691,38546,618
Chlamydia trachomatis infection11,02428,56231,0891,425,303
Giardiasis11523033511,870
Gonorrhea3,2077,1558,283369,926

The current Morbidity and Mortality Weekly Report is available online.

Exercise (PageIndex{5})

Describe how health agencies obtain data about the incidence of diseases of public health importance.

The World Health Organization (WHO)

A large number of international programs and agencies are involved in efforts to promote global public health. Among their goals are developing infrastructure in health care, public sanitation, and public health capacity; monitoring infectious disease occurrences around the world; coordinating communications between national public health agencies in various countries; and coordinating international responses to major health crises. In large part, these international efforts are necessary because disease-causing microorganisms know no national boundaries.

International public health issues are coordinated by the World Health Organization (WHO), an agency of the United Nations. Of its roughly $4 billion budget for 2015–165, about $1 billion was funded by member states and the remaining $3 billion by voluntary contributions. In addition to monitoring and reporting on infectious disease, WHO also develops and implements strategies for their control and prevention. WHO has had a number of successful international public health campaigns. For example, its vaccination program against smallpox, begun in the mid-1960s, resulted in the global eradication of the disease by 1980. WHO continues to be involved in infectious disease control, primarily in the developing world, with programs targeting malaria, HIV/AIDS, and tuberculosis, among others. It also runs programs to reduce illness and mortality that occur as a result of violence, accidents, lifestyle-associated illnesses such as diabetes, and poor health-care infrastructure.

WHO maintains a global alert and response system that coordinates information from member nations. In the event of a public health emergency or epidemic, it provides logistical support and coordinates international response to the emergency. The United States contributes to this effort through the CDC. The CDC carries out international monitoring and public health efforts, mainly in the service of protecting US public health in an increasingly connected world. Similarly, the European Union maintains a Health Security Committee that monitors disease outbreaks within its member countries and internationally, coordinating with WHO.

Exercise (PageIndex{6})

Name the organizations that participate in international public health monitoring.

Emerging and Reemerging Infectious Diseases

Both WHO and some national public health agencies such as the CDC monitor and prepare for emerging infectious diseases. An emerging infectious disease is either new to the human population or has shown an increase in prevalence in the previous twenty years. Whether the disease is new or conditions have changed to cause an increase in frequency, its status as emerging implies the need to apply resources to understand and control its growing impact.

Emerging diseases may change their frequency gradually over time, or they may experience sudden epidemic growth. The importance of vigilance was made clear during the Ebola hemorrhagic fever epidemic in western Africa through 2014–2015. Although health experts had been aware of the Ebola virus since the 1970s, an outbreak on such a large scale had never happened before (Figure (PageIndex{5})). Previous human epidemics had been small, isolated, and contained. Indeed, the gorilla and chimpanzee populations of western Africa had suffered far worse from Ebola than the human population. The pattern of small isolated human epidemics changed in 2014. Its high transmission rate, coupled with cultural practices for treatment of the dead and perhaps its emergence in an urban setting, caused the disease to spread rapidly, and thousands of people died. The international public health community responded with a large emergency effort to treat patients and contain the epidemic.

Emerging diseases are found in all countries, both developed and developing (Table (PageIndex{3})). Some nations are better equipped to deal with them. National and international public health agencies watch for epidemics like the Ebola outbreak in developing countries because those countries rarely have the health-care infrastructure and expertise to deal with large outbreaks effectively. Even with the support of international agencies, the systems in western Africa struggled to identify and care for the sick and control spread. In addition to the altruistic goal of saving lives and assisting nations lacking in resources, the global nature of transportation means that an outbreak anywhere can spread quickly to every corner of the planet. Managing an epidemic in one location—its source—is far easier than fighting it on many fronts.

Ebola is not the only disease that needs to be monitored in the global environment. In 2015, WHO set priorities on several emerging diseases that had a high probability of causing epidemics and that were poorly understood (and thus urgently required research and development efforts).

A reemerging infectious disease is a disease that is increasing in frequency after a previous period of decline. Its reemergence may be a result of changing conditions or old prevention regimes that are no longer working. Examples of such diseases are drug-resistant forms of tuberculosis, bacterial pneumonia, and malaria. Drug-resistant strains of the bacteria causing gonorrhea and syphilis are also becoming more widespread, raising concerns of untreatable infections.

Table (PageIndex{3}): Some Emerging and Reemerging Infectious Diseases

DiseasePathogenYear DiscoveredAffected RegionsTransmission
AIDSHIV1981WorldwideContact with infected body fluids
Chikungunya feverChikungunya virus1952Africa, Asia, India; spreading to Europe and the AmericasMosquito-borne
Ebola virus diseaseEbola virus1976Central and Western AfricaContact with infected body fluids
H1N1 Influenza (swine flu)H1N1 virus2009WorldwideDroplet transmission
Lyme diseaseBorrelia burgdorferi bacterium1981Northern hemisphereFrom mammal reservoirs to humans by tick vectors
West Nile virus diseaseWest Nile virus1937Africa, Australia, Canada to Venezuela, Europe, Middle East, Western AsiaMosquito-borne

Exercise (PageIndex{7})

  1. Explain why it is important to monitor emerging infectious diseases.
  2. Explain how a bacterial disease could reemerge, even if it had previously been successfully treated and controlled.

SARS Outbreak and Identification

On November 16, 2002, the first case of a SARS outbreak was reported in Guangdong Province, China. The patient exhibited influenza-like symptoms such as fever, cough, myalgia, sore throat, and shortness of breath. As the number of cases grew, the Chinese government was reluctant to openly communicate information about the epidemic with the World Health Organization (WHO) and the international community. The slow reaction of Chinese public health officials to this new disease contributed to the spread of the epidemic within and later outside China. In April 2003, the Chinese government finally responded with a huge public health effort involving quarantines, medical checkpoints, and massive cleaning projects. Over 18,000 people were quarantined in Beijing alone. Large funding initiatives were created to improve health-care facilities, and dedicated outbreak teams were created to coordinate the response. By August 16, 2003, the last SARS patients were released from a hospital in Beijing nine months after the first case was reported in China.

In the meantime, SARS spread to other countries on its way to becoming a global pandemic. Though the infectious agent had yet to be identified, it was thought to be an influenza virus. The disease was named SARS, an acronym for severe acute respiratory syndrome, until the etiologic agent could be identified. Travel restrictions to Southeast Asia were enforced by many countries. By the end of the outbreak, there were 8,098 cases and 774 deaths worldwide. China and Hong Kong were hit hardest by the epidemic, but Taiwan, Singapore, and Toronto, Canada, also saw significant numbers of cases (Figure (PageIndex{6})).

Fortunately, timely public health responses in many countries effectively suppressed the outbreak and led to its eventual containment. For example, the disease was introduced to Canada in February 2003 by an infected traveler from Hong Kong, who died shortly after being hospitalized. By the end of March, hospital isolation and home quarantine procedures were in place in the Toronto area, stringent anti-infection protocols were introduced in hospitals, and the media were actively reporting on the disease. Public health officials tracked down contacts of infected individuals and quarantined them. A total of 25,000 individuals were quarantined in the city. Thanks to the vigorous response of the Canadian public health community, SARS was brought under control in Toronto by June, a mere four months after it was introduced.

In 2003, WHO established a collaborative effort to identify the causative agent of SARS, which has now been identified as a coronavirus that was associated with horseshoe bats. The genome of the SARS virus was sequenced and published by researchers at the CDC and in Canada in May 2003, and in the same month researchers in the Netherlands confirmed the etiology of the disease by fulfilling Koch’s postulates for the SARS coronavirus. The last known case of SARS worldwide was reported in 2004.

This database of reports chronicles outbreaks of infectious disease around the world. It was on this system that the first information about the SARS outbreak in China emerged.

The CDC publishes Emerging Infectious Diseases, a monthly journal available online.

Key Concepts and Summary

  • Epidemiology is the science underlying public health.
  • Morbidity means being in a state of illness, whereas mortality refers to death; both morbidity rates and mortality rates are of interest to epidemiologists.
  • Incidence is the number of new cases (morbidity or mortality), usually expressed as a proportion, during a specified time period; prevalence is the total number affected in the population, again usually expressed as a proportion.
  • Sporadic diseases only occur rarely and largely without a geographic focus. Endemic diseases occur at a constant (and often low) level within a population. Epidemic diseases and pandemic diseases occur when an outbreak occurs on a significantly larger than expected level, either locally or globally, respectively.
  • Koch’s postulates specify the procedure for confirming a particular pathogen as the etiologic agent of a particular disease. Koch’s postulates have limitations in application if the microbe cannot be isolated and cultured or if there is no animal host for the microbe. In this case, molecular Koch’s postulates would be utilized.
  • In the United States, the Centers for Disease Control and Prevention monitors notifiable diseases and publishes weekly updates in the Morbidity and Mortality Weekly Report.
  • The World Health Organization (WHO) is an agency of the United Nations that collects and analyzes data on disease occurrence from member nations. WHO also coordinates public health programs and responses to international health emergencies.
  • Emerging diseases are those that are new to human populations or that have been increasing in the past two decades. Reemerging diseases are those that are making a resurgence in susceptible populations after previously having been controlled in some geographic areas.

Footnotes

  1. H. Irene Hall, Qian An, Tian Tang, Ruiguang Song, Mi Chen, Timothy Green, and Jian Kang. “Prevalence of Diagnosed and Undiagnosed HIV Infection—United States, 2008–2012.” Morbidity and Mortality Weekly Report 64, no. 24 (2015): 657–662.
  2. Centers for Disease Control and Prevention. “Diagnoses of HIV Infection in the United States and Dependent Areas, 2014.” HIV Surveillance Report 26 (2015).
  3. Centers for Disease Control and Prevention. “Tetanus Surveillance—United States, 2001–2008.” Morbidity and Mortality Weekly Report 60, no. 12 (2011): 365.
  4. Centers for Disease Control and Prevention. “Plague in the United States.” 2015. http://www.cdc.gov/plague/maps. Accessed June 1, 2016.
  5. World Health Organization. “Programme Budget 2014–2015.” www.who.int/about/finances-ac...lity/budget/en.

Epidemiologist Overview

An epidemiologist is a scientist who studies disease and other factors that affect public health. Although the public is most familiar with epidemiologists that specialize in infectious diseases, other epidemiologists specialize in injuries, maternal health, and other aspects of public health. Epidemiologists spend a lot of their time doing research. They analyze samples in labs and collect data on the frequency of certain diseases among different populations. However, epidemiologists don't spend all of their time with microscopes and data programs. They use their knowledge to advise governments and the public on public health measures. They may work with local officials to develop a pandemic response protocol or help private businesses implement wellness programs that will minimize workplace injuries.

Epidemiologists are usually required to have a master's degree in public health. Some epidemiologists are medical doctors that complete a program in epidemiology at the same time. Academic knowledge is not enough. Epidemiologists also need to have practical experience in the form of a public health internship or residency.

Epidemiologists earn an average salary of $60,681 a year. Most are not in this field for the money but for the satisfaction of saving lives.

What Does an Epidemiologist Do

Epidemiologists are public health professionals who investigate patterns and causes of disease and injury in humans. They seek to reduce the risk and occurrence of negative health outcomes through research, community education and health policy.

Epidemiologists typically do the following:

  • Plan and direct studies of public health problems to find ways to prevent and to treat them if they arise
  • Collect and analyze data—through observations, interviews, and surveys, and by using samples of blood or other bodily fluids—to find the causes of diseases or other health problems
  • Communicate their findings to health practitioners, policymakers, and the public
  • Manage public health programs by planning programs, monitoring their progress, analyzing data, and seeking ways to improve the programs in order to improve public health outcomes
  • Supervise professional, technical, and clerical personnel

Epidemiologists collect and analyze data to investigate health issues. For example, an epidemiologist might collect and analyze demographic data to determine who is at the highest risk for a particular disease. They also may research and investigate the trends in populations of survivors of certain diseases, such as cancer, so that effective treatments can be identified and repeated across the population.

Epidemiologists typically work either in applied public health or in research. Applied epidemiologists work for state and local governments, addressing public health problems directly. They often are involved with education outreach and survey efforts in communities. Research epidemiologists typically work for universities or in affiliation with federal agencies, such as the Centers for Disease Control and Prevention (CDC) or the National Institutes of Health (NIH).

Epidemiologists who work in private industry commonly conduct research for health insurance companies or pharmaceutical companies. Those in nonprofit companies often do public health advocacy work. Epidemiologists involved in research are rarely advocates, because scientific research is expected to be unbiased.

Epidemiologists typically specialize in one or more of the following public health areas:

  • Infectious diseases
  • Public health preparedness and emergency response
  • Maternal and child health
  • Chronic diseases
  • Environmental health
  • Injury
  • Occupational health
  • Behavioral epidemiology
  • Oral health

For more information on occupations that concentrate on the biological workings of disease or the effects of disease on individuals, see the profiles for biochemists and biophysicists, medical scientists, microbiologists, and physicians and surgeons.

How To Become an Epidemiologist

Epidemiologists need at least a master’s degree from an accredited college or university. Most epidemiologists have a master’s degree in public health (MPH) or a related field, and some have completed a doctoral degree in epidemiology or medicine.

Epidemiologists typically need at least a master’s degree from an accredited college or university. A master’s degree in public health with an emphasis in epidemiology is most common, but epidemiologists can earn degrees in a wide range of related fields and specializations. Epidemiologists who direct research projects—including those who work as postsecondary teachers in colleges and universities—have a Ph.D. or medical degree in their chosen field.

Coursework in epidemiology includes classes in public health, biological and physical sciences, and math and statistics. Classes emphasize statistical methods, causal analysis, and survey design. Advanced courses emphasize multiple regression, medical informatics, reviews of previous biomedical research, comparisons of healthcare systems, and practical applications of data.

Many master’s degree programs in public health, as well as other programs that are specific to epidemiology, require students to complete an internship or practicum that typically ranges from a semester to a year.

Some epidemiologists have both a degree in epidemiology and a medical degree. These scientists often work in clinical capacities. In medical school, students spend most of their first 2 years in laboratories and classrooms, taking courses such as anatomy, biochemistry, physiology, pharmacology, psychology, microbiology, and pathology. Medical students also have the option to choose electives such as medical ethics and medical laws. They also learn to take medical histories, examine patients, and diagnose illnesses.

Important Qualities

Communication skills. Epidemiologists must use their speaking and writing skills to inform the public and community leaders about public health risks. Clear communication also is required for an epidemiologist to work effectively with other health professionals.

Critical-thinking skills. Epidemiologists analyze data to determine how best to respond to a public health problem or an urgent health-related emergency.

Detail oriented. Epidemiologists must be precise and accurate in moving from observation and interview to conclusions.

Math and statistical skills. Epidemiologists may need advanced math and statistical skills in designing and administering studies and surveys. Skill in using large databases and statistical computer programs may also be important.

Teaching skills. Epidemiologists may be involved in community outreach activities that educate the public about health risks and healthy living.

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  • Developed an innovative emergency department discharge database, containing more than 600,000 records annually.
  • Collaborate with City, County and State government officials on emergency preparedness procedures.
  • Co-facilitated the Public Health Emergency Response team during communicable disease outbreaks, and other public health events, i.e.
  • Participate in exercises, responses, and planning efforts led by the Maine Office of Public Health Emergency Preparedness.
  • Created a culture of collaboration between acute care hospitals with emergency departments, which became a national model.
  • Analyzed birth, death, Emergency Dept.
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  • Served as the Norfolk Public Health Emergency Response Team "Hazmat for Healthcare" Awareness Level and Operations Level Trainer.

Public Health (PB HLTH)

Terms offered: Spring 2016, Spring 2015, Spring 2014
Introduction to personal and community health, drawing on physical and social sciences. Specific areas include stress, alcohol and drugs, nutrition, exercise, the environment, communication, and sexuality. Readings, lectures, and discussions explore key issues for students and examine those issues in the context of contemporary American society. Public health approaches to disease prevention and health promotion are explored for each top ic.
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This seminar provides an overview of the intersection between global health and social justice, with a specific focus on the ways in which inequity, specifically the conditions that lead to poverty, disproportionately affect health outcomes. Students will learn about the historical and theoretical underpinnings of global health, how social determinants affect medical outcomes and health policy, the principles of international law and health economics, and the structure of health delivery models. In the process, students will engage in topics related to social factors that impact health, including class, race, gender, and poverty. Class discussions will address contemporary global health priorities through the lens of human rights activism.
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PB HLTH㺘 Freshman Seminar in Public Health 1 Unit

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Repeat rules: Course may be repeated for credit without restriction.

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Rules & Requirements

Prerequisites: At discretion of instructor

Repeat rules: Course may be repeated for credit when topic changes.

Hours & Format

Fall and/or spring:
5 weeks - 3-6 hours of seminar per week
10 weeks - 1.5-3 hours of seminar per week
15 weeks - 1-2 hours of seminar per week

Summer:
6 weeks - 2.5-5 hours of seminar per week
8 weeks - 1.5-3.5 hours of seminar and 2-4 hours of seminar per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: The grading option will be decided by the instructor when the class is offered. Final Exam To be decided by the instructor when the class is offered.

PB HLTH㻢 Directed Group Study 1 - 4 Units

Terms offered: Spring 2016, Fall 2015, Spring 2015

Directed Group Study: Read More [+]

Rules & Requirements

Credit Restrictions: Enrollment is restricted see the Introduction to Courses and Curricula section of this catalog.

Repeat rules: Course may be repeated for credit without restriction.

Hours & Format

Fall and/or spring: 15 weeks - 1-4 hours of directed group study per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Offered for pass/not pass grade only. Final exam not required.

PB HLTH㻣 Supervised Independent Study 1 - 4 Units

Rules & Requirements

Prerequisites: Consent of instructor

Hours & Format

Fall and/or spring: 15 weeks - 1-4 hours of independent study per week

Summer:
6 weeks - 2.5-10 hours of independent study per week
8 weeks - 1.5-7.5 hours of independent study per week
10 weeks - 1.5-6 hours of independent study per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Offered for pass/not pass grade only. Final exam not required.

PB HLTH𧅥 A Sustainable World: Challenges and Opportunities 3 Units

Terms offered: Fall 2021, Spring 2021, Fall 2020
Human activity and human numbers threaten the possibility of irreversible damage to the fragile biosphere on which all life depends. The current generation of students is the first one to face this existential problem and it may be the last one that can solve it. The goal of this course is for faculty with expertise in the many variables involved-energy consumption, food security, population growth and family planning, climate change, governance , migration, resource consumption, etc.-to give one-hour presentations on their specific topic. Teacher Scholars supervised by a GSI will facilitate student discussion groups, who will then prepare brief statements responding to the challenge presented, and suggest ways of ameliorating the problems
A Sustainable World: Challenges and Opportunities: Read More [+]

Hours & Format

Fall and/or spring: 15 weeks - 2 hours of lecture and 1 hour of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Alternate method of final assessment during regularly scheduled final exam group (e.g., presentation, final project, etc.).

Instructor: Potts

PB HLTH𧅨A Health Promotion in a College Setting 2 Units

Terms offered: Fall 2016, Fall 2015, Fall 2014
Topics include health promotion, medical self-care, and delivery of health care service. Through a combined theory and practice approach, topics are covered as they apply to the campus community. The course is divided into three sections corresponding to particular campus health field experiences in which students may be involved.
Health Promotion in a College Setting: Read More [+]

Rules & Requirements

Prerequisites: Consent of instructor

Repeat rules: Course may be repeated for credit without restriction.

Hours & Format

Fall and/or spring: 15 weeks - 1.5 hours of lecture and 1 hour of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Offered for pass/not pass grade only. Final exam not required.

Instructor: Kodama

PB HLTH𧅨B Health Promotion in a College Setting 2 Units

Terms offered: Spring 2017, Spring 2016, Spring 2015
Topics include health promotion, medical self-care, and delivery of health care service. Through a combined theory and practice approach, topics are covered as they apply to the campus community. The course is divided into three sections corresponding to particular campus health field experiences in which students may be involved.
Health Promotion in a College Setting: Read More [+]

Rules & Requirements

Prerequisites: Consent of instructor

Repeat rules: Course may be repeated for credit without restriction.

Hours & Format

Fall and/or spring: 15 weeks - 1.5 hours of lecture and 1 hour of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Offered for pass/not pass grade only. Final exam not required.

Instructor: Kodama

PB HLTH𧅫 Violence, Social Justice, and Public Health 2 Units

Terms offered: Summer 2021 First 6 Week Session, Summer 2020 First 6 Week Session, Summer 2019 First 6 Week Session
This course addresses violence as a public health issue, using an interdisciplinary public health approach to enable undergraduate students to explore and analyze violence from personal, social, community and political perspectives. Students will learn to apply public health strategies to identify causes of violence and develop practical community-based plans to prevent violence and promote safety. This course will examine violence through the lens of the college campus, paying particular attention to the types of violence more commonly seen on, or associated with, collegiate life, and will include a term paper component.
Violence, Social Justice, and Public Health: Read More [+]

Hours & Format

Fall and/or spring: 15 weeks - 2 hours of lecture per week

Summer: 6 weeks - 6 hours of lecture per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Alternate method of final assessment during regularly scheduled final exam group (e.g., presentation, final project, etc.).

Instructor: Gamble

PB HLTH W108 Women's Health, Gender And Empowerment 3 Units

Terms offered: Spring 2021, Spring 2020, Spring 2019
The course will provide core knowledge and skills from several disciplines on how to improve women's health and well-being globally, and it will follow a life course framework. It aims to expand students’ understanding of the interconnected factors that influence women’s health and empowerment - including foundations of sexual and reproductive health, economic development, political frameworks and global reproductive rights, demographic and social changes, basic principles of empowerment theory, educational opportunities, and efforts to ensure gender equity.
Women's Health, Gender And Empowerment: Read More [+]

Objectives & Outcomes

Course Objectives: A.[KNOWLEDGE]: To expand students’ understanding of the interconnected cultural, demographic, social, and economic factors that influence women’s health and empowerment globally.
B.[KNOWLEDGE]: To gain knowledge of the historical and present-day contexts of politics, policies, and laws related to women’s health outcomes, human rights, sexual and reproductive rights, and gender inequities.
C.[SKILLS]: To critically engage with contrasting perspectives and changing paradigms about women’s health and empowerment among epidemiologists, clinicians, public health experts, demographers, economists, human rights activists, and development specialists.
D.[SKILLS]: Assess policies, development frameworks and case studies of interventions designed to improve women’s health and empowerment in differing cultural and national contexts with specific attention to gender norms.

Student Learning Outcomes: Analyze case studies applying the relevant historical context of politics, policies, and laws related to women’s health and human rights.
Analyze the contrasting perspectives and changing paradigms among epidemiologists, public health experts, demographers, economists, human rights activists and development specialists related to women’s health and empowerment
Assess the impact of women’s health on advances in other sectors including child health, education, economic development, and social stability
Compare macro level political, institutional, and structural factors that influence women’s health and empowerment in relation to local, cultural, and regional contexts
Critically examine how gender and women’s empowerment is addressed in the Sustainable Development Goals and other development frameworks
Evaluate case studies of interventions designed to improve women’s health and empowerment in differing cultural and national contexts and recommend improvements
Examine how girls’ education contributes to individual, community, and national development.
Explain the ways in which social, economic, and cultural factors can both promote and impede women’s and girls’ health.
Identify the major institutions and non-governmental organizations that influence women’s health and empowerment and suitable approaches for implementing interventions to ensure gender equity
Identify and analyze gender inequities in health care needs and access to care.

Hours & Format

Fall and/or spring: 15 weeks - 1.5 hours of web-based lecture and 1 hour of web-based discussion per week

Online: This is an online course.

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Alternative to final exam.

Instructors: Hemmerling, Decker, Mindry

PB HLTH𧅰 Global Health: A Multidisciplinary Examination 4 Units

Terms offered: Summer 2017 First 6 Week Session, Spring 2016, Spring 2015
This course examines health at the individual and community/global level by examining the interplay of many factors, including the legal, social, political, and physical environments economic forces access to food, safe water, sanitation, and affordable preventive/medical care nutrition cultural beliefs and human behaviors and religion among others. Students will be expected to read, understand, and use advanced materials from diverse disciplines. Class accompanied by case-based discussions.
Global Health: A Multidisciplinary Examination: Read More [+]

Rules & Requirements

Credit Restrictions: Students who complete PH N112 receive no credit for completing PH 112

Hours & Format

Fall and/or spring: 15 weeks - 3 hours of lecture and 1 hour of discussion per week

Summer: 6 weeks - 9 hours of lecture and 3 hours of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructors: Krishnan, Reingold

PB HLTH N112 Global Health: A Multidisciplinary Examination 4 Units

Terms offered: Summer 2021 First 6 Week Session, Summer 2020 First 6 Week Session, Summer 2019 First 6 Week Session
This course examines health at the individual and community/global level by examining the interplay of many factors, including the legal, social, political, and physical environments economic forces access to food, safe water, sanitation, and affordable preventive/medical care nutrition cultural beliefs and human behaviors and religion among others. Students will be expected to read, understand, and use advanced materials from diverse disciplines. Class accompanied by case-based discussions.
This class is the Summer Session version of PH 112 same units and content, increased lecture and discussion hours.
Global Health: A Multidisciplinary Examination: Read More [+]

Rules & Requirements

Credit Restrictions: Students who complete PH 112 receive no credit for completing PH N112.

Hours & Format

Summer: 6 weeks - 6 hours of lecture and 6 hours of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructors: Reingold, Colford

PB HLTH𧅳 Introduction to Global Health Equity 3 Units

Terms offered: Summer 2021 Second 6 Week Session, Summer 2020 Second 6 Week Session
This lecture will provide an overview of the intersection between global health and social justice, with a specific focus on ways in which inequity, specifically conditions that lead to poverty, disproportionately affect health outcomes. Students will learn about historical and theoretical underpinnings of global health, how social and structural determinants affect health outcomes and policy, the principles of international law and health economics, and the structure of health delivery models. In the process, students will engage in topics related to social factors that impact health, including class, race, gender, and poverty. Class discussions will address contemporary global health priorities through the lens of human rights activism.
Introduction to Global Health Equity: Read More [+]

Objectives & Outcomes

Student Learning Outcomes: Critically analyze and critique key grassroots global health advocacy efforts and models
Formulate comprehensive and equitable policy recommendations on global health cases
Think critically about and articulate the history, pathology, and causation of contemporary global health inequity
Utilize basic research methods and work collaboratively in a team setting to complete a group case project

Rules & Requirements

Credit Restrictions: Students will receive no credit for PB HLTH𧅳 after completing PB HLTH㺏. A deficient grade in PB HLTH𧅳 may be removed by taking PB HLTH㺏.

Repeat rules: Course may be repeated for credit with advisor consent.

Hours & Format

Summer: 6 weeks - 4 hours of lecture and 4 hours of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructor: Le

PB HLTH𧅴 Seminar on Social, Political, and Ethical Issues in Health and Medicine 3 Units

Terms offered: Fall 2021, Spring 2021, Fall 2020
This course offers an introduction to issues and perspectives related to health and medicine. Guest lecturers speak about the week’s topic, which can include a variety of topics such as public health, violence, chronic illnesses, environmental health, and health care economics. Speakers share their first-hand experiences in their fields, discuss current issues, debate ethical dilemmas, and pose and answer questions. During the weekly discussion sections, students delve deeper into the issues, not only exploring and perhaps questioning their own thoughts and beliefs, but also learning from the experiences and perspectives of their fellow students.
Seminar on Social, Political, and Ethical Issues in Health and Medicine: Read More [+]

Hours & Format

Fall and/or spring: 15 weeks - 2 hours of lecture and 1 hour of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Offered for pass/not pass grade only. Final exam required.

Instructor: Potts

PB HLTH C117 Introduction to Global Health Disparities Research 2 Units

Terms offered: Spring 2020, Spring 2019, Spring 2018
This course prepares students to conduct a 10-week global health research project in a low or middle-income country (LMIC) provides a background in global health, emphasizing infectious disease research, international research ethics, and the conduct of health research in low-resource settings. Leads students through the process of preparing for, conducting, and completing a short-term research project, with modules focused on cultural communication , the role and pace of research in these other countries, presentation preparation, project development, and troubleshooting skills gaining perspective into the relationship between global health and health disparities in the USA
Introduction to Global Health Disparities Research: Read More [+]

Hours & Format

Fall and/or spring: 15 weeks - 2 hours of lecture per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Alternate method of final assessment during regularly scheduled final exam group (e.g., presentation, final project, etc.).

Instructor: Reingold

Also listed as: INTEGBI C195

PB HLTH𧅶 Nutrition in Developing Countries 3 Units

Terms offered: Summer 2021 First 6 Week Session, Spring 2021, Summer 2020 First 6 Week Session
We will focus on low- and middle-income countries because they experience the greatest burden of malnutrition, and because they face a unique context of limited financial and government resources. In this course, we will discuss the effects of nutrition throughout the lifecycle in pregnancy, infancy, childhood, and adulthood. We will focus on nutrition broadly including issues of undernutrition, micronutrient deficiencies, and obesity. We will also analyze and evaluate actions taken to ameliorate the major nutritional problems facing vulnerable populations in low- and middle-income countries.
Nutrition in Developing Countries: Read More [+]

Hours & Format

Fall and/or spring: 15 weeks - 3 hours of lecture per week

Summer: 6 weeks - 8 hours of lecture per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Alternative to final exam.

Instructor: Fernald

PB HLTH𧅾 Health Economics and Public Policy 3 Units

Terms offered: Spring 2021, Spring 2020, Spring 2019
This course focuses on a selected set of the major health policy issues and uses economics to uncover and better understand the issues. The course examines the scope for government intervention in health markets.
Health Economics and Public Policy: Read More [+]

Rules & Requirements

Prerequisites: Public Health major or consent of instructor

Hours & Format

Fall and/or spring: 15 weeks - 3 hours of lecture and 1 hour of discussion per week

Summer: 8 weeks - 6 hours of lecture and 2 hours of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructor: Fulton

PB HLTH𧆁 The Aging Human Brain 3 Units

Terms offered: Fall 2021, Fall 2019, Fall 2017
The course will survey the field of the human brain, with introductory lectures on the concepts of aging, and brief surveys of normal neuroanatomy, neurophysiology, neurochemistry, and neuropsychology as well as methods such as imaging, epidemiology, and pathology. The neurobiological changes associated with aging will be covered from the same perspectives: neuropsychology, anatomy, biochemistry, and physiology. Major neurological diseases of aging including Alzheimer's and Parkinson's disease will be covered, as will compensatory mechanisms, neuroendocrine changes with aging, depression and aging, epidemiology of aging, and risk factors for decline.
The Aging Human Brain: Read More [+]

Hours & Format

Fall and/or spring: 15 weeks - 2 hours of lecture and 1 hour of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required, with common exam group.

Instructor: Jagust

PB HLTH𧆂 Advanced Health Policy 3 Units

Terms offered: Spring 2021, Spring 2020, Spring 2019
This course will give you the opportunity to build upon your understanding of the organization, financing and current policy issues of the US health care delivery system obtained in PH 150D. In this course you will become engaged health policy analysts, applying policy making tools (e.g., policy memos/briefs, legislative analysis, regulatory comments, media advocacy, public testimony) to actual health issues and problems. Through individual and group work, you will draw upon both verbal and written communication skills to effectuate health policy change.
Advanced Health Policy: Read More [+]

Rules & Requirements

Prerequisites: PH 150D: Introduction to Health Policy and Management

Hours & Format

Fall and/or spring: 15 weeks - 2 hours of lecture and 1 hour of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Alternative to final exam.

Instructor: Flagg

PB HLTH𧆄 Artificial Intelligence for Health and Healthcare 3 Units

Terms offered: Fall 2021
Over the coming decades, data and algorithms will transform medicine and our health care system. Whether you plan to be a doctor, an algorithm developer, or a manager or policy maker in the health sector, this course will help you understand: (1) the tremendous upside of artificial intelligence for health, and (2) how well-intentioned efforts to apply these tools can do harm. The course will be quantitative (e.g., technical readings problem sets requiring statistical software), and is designed for students with at least intermediate coursework in statistics, economics, computer science,etc.
Artificial Intelligence for Health and Healthcare: Read More [+]

Objectives & Outcomes

Course Objectives: Finally, students will learn to identify new unsolved problems where data and algorithms could improve health and medicine, and start to think about developing solutions.
Students will also come away with a list of several ‘red flags’ -- unique challenges of health data that make it difficult to apply algorithms that have been successful in other fields. This will help them become better and more critical consumers of literature and news in this area.
Students will learn about several problems in health care where artificial intelligence is helping doctors and policy makers.

Rules & Requirements

Prerequisites: An intermediate coursework in statistics (e.g., C100), economics(e.g., 100A/B), computer science(e.g., CS88), etc. is recommended

Hours & Format

Fall and/or spring: 15 weeks - 1.5 hours of lecture and 1.5 hours of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Alternative to final exam.

Instructor: Obermeyer

PB HLTH𧆍 Introduction to Biostatistics 5 Units

Terms offered: Summer 2017 Second 6 Week Session, Summer 2016 10 Week Session, Summer 2016 Second 6 Week Session
An intensive introductory course in statistical methods used in applied research. Emphasis on principles of statistical reasoning, underlying assumptions, and careful interpretation of results. Topics covered: descriptive statistics, graphical displays of data, introduction to probability, expectations and variance of ramdom variables, confidence intervals and tests for means, differences of means, proportions, differences of proportions, chi-square tests for categorical variables, regression and multiple regression, an introduction to analysis of variance. Statistical software will be used to supplement hand calculation. Students who successfully complete Public Health 141 are prepared to continue their biostatistics course work in 200-level courses. With the approval of their degree program, MPH students may use Public Health 141 to fulfill the biostatistics course requirement (contact program manager for approval). Public Health 141 also fulfills the biostatistics course requirement for the Public Health Undergraduate Major.
Introduction to Biostatistics: Read More [+]

Rules & Requirements

Prerequisites: High school algebra

Hours & Format

Fall and/or spring: 15 weeks - 3 hours of lecture, 1 hour of discussion, and 2 hours of laboratory per week

Summer: 6 weeks - 12.5 hours of lecture and 7.5 hours of laboratory per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

PB HLTH𧆎 Introduction to Probability and Statistics in Biology and Public Health 4 Units

Terms offered: Fall 2021, Summer 2021 Second 6 Week Session, Spring 2021
Descriptive statistics, probability, probability distributions, point and interval estimation, hypothesis testing, chi-square, correlation and regression with biomedical applications.
Introduction to Probability and Statistics in Biology and Public Health: Read More [+]

Rules & Requirements

Prerequisites: High school algebra

Hours & Format

Fall and/or spring: 15 weeks - 3 hours of lecture, 1 hour of discussion, and 1 hour of laboratory per week

Summer: 6 weeks - 7.5 hours of lecture, 2.5 hours of discussion, and 2.5 hours of laboratory per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructor: Selvin

PB HLTH W142 Introduction to Probability and Statistics in Biology and Public Health 4 Units

Terms offered: Spring 2021, Spring 2020, Spring 2019
Descriptive statistics, probability, probability distributions, point and interval estimation, hypothesis testing, chi-square, correlation, and regression with biomedical applications.
Introduction to Probability and Statistics in Biology and Public Health: Read More [+]

Hours & Format

Fall and/or spring: 7 weeks - 8 hours of web-based lecture per week

Online: This is an online course.

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam not required.

Instructor: Lahiff

PB HLTH𧆐A Introduction to SAS Programming 2 Units

Terms offered: Spring 2016, Spring 2015, Spring 2014
This course is intended to serve as an introduction to the SAS programming language for Windows in an applied, workshop environment. Emphasis is on data management and programming in a public health research setting. Topics include SAS language to compute, recode, label, and format variables as well as sort, subset, concatenate, and merge data sets. SAS statistical procedures will be used to compute univariate and bivariate summary statistics and tests, simple linear models,graphical plots, and statistical output data sets.
Introduction to SAS Programming: Read More [+]

Rules & Requirements

Prerequisites: 142 or consent of instructor

Credit Restrictions: This course (or equivalent) is required for students who plan to enroll in 251, Practicum in Epidemiological Methods. Enrollment is limited to School of Public Health students. If space permits, others may enroll with consent of instructor.

Hours & Format

Fall and/or spring: 8 weeks - 2 hours of lecture and 3 hours of laboratory per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructor: Lein

PB HLTH𧆐B Intermediate SAS Programming 2 Units

Terms offered: Spring 2016, Spring 2015, Spring 2014
Topics include data step flow control, looping and automated processing, implicit and explicit arrays, data simulation strategies, data set reconfiguration, use of SAS Macro variables, and writing simple SAS Macro programs.
Intermediate SAS Programming: Read More [+]

Rules & Requirements

Prerequisites: 144A

Credit Restrictions: Enrollment is limited to School of Public Health students. If space permits, others may enroll with consent of instructor.

Hours & Format

Fall and/or spring: 8 weeks - 2 hours of lecture and 3 hours of laboratory per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructor: Lein

PB HLTH𧆑 Statistical Analysis of Continuous Outcome Data 4 Units

Terms offered: Fall 2016, Fall 2015, Spring 2013
Regression models for continuous outcome data: least squares estimates and their properties, interpreting coefficients, prediction, comparing models, checking model assumptions, transformations, outliers, and influential points. Categorical explanatory variables: interaction and analysis of covariance, correlation and partial correlation. Appropriate graphical methods and statistical computing. Analysis of variance for one- and two-factor models: F tests, assumption checking, multiple comparisons. Random effects models and variance components. Introduction to repeated measures models.
Statistical Analysis of Continuous Outcome Data: Read More [+]

Rules & Requirements

Prerequisites: 142 or equivalent

Hours & Format

Fall and/or spring: 15 weeks - 3 hours of lecture and 2 hours of laboratory per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructor: Lahiff

Formerly known as: 142B

PB HLTH𧆓 Global Perspective on Vision 2 Units

Terms offered: Spring 2021, Spring 2020, Spring 2019
There are four facets to the course. 1) Core knowledge of the epidemiology of the major causes of vision loss globally 2) The role of ophthalmology and surgical interventions in global health 3) novel teaching methods in group dynamics, public speaking, video making, physician shadowing, surgery observation and leadership opportunities 4) Hands on public health work with an intervention, such as vision screening for the homeless. A multidisciplinary approach will be employed to study what interventions are taking place to alleviate the burden of ophthalmic disease.
Global Perspective on Vision: Read More [+]

Hours & Format

Fall and/or spring: 15 weeks - 2 hours of lecture per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructor: Lee

Formerly known as: Public Health 247

PB HLTH𧆖A Introduction to Epidemiology and Human Disease 4 Units

Terms offered: Spring 2021, Spring 2020, Spring 2019
This course introduces epidemiological methods with the goal of teaching students to read critically and interpret published epidemiologic studies in humans. The course also exposes students to the epidemiology of diseases and conditions of current public health importance in the United States and internationally.
Introduction to Epidemiology and Human Disease: Read More [+]

Rules & Requirements

Prerequisites: A course in statistics, preferably 142

Hours & Format

Fall and/or spring: 15 weeks - 4 hours of lecture and 1 hour of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructors: Abrams, Barcellos, Buffler

Formerly known as: 150

PB HLTH𧆖B Human Health and the Environment in a Changing World 3 Units

Terms offered: Fall 2021, Fall 2020, Fall 2019
The course will present the major human and natural activities that lead to release of hazardous materials into the environment as well as the causal links between chemical, physical, and biological hazards in the environment and their impact on human health. The basic principles of toxicology will be presented including dose-response relationships, absorption, distribution, metabolism, and excretion of chemicals. The overall role of environmental risks in the pattern of human disease, both nationally and internationally, will be covered. The engineering and policy strategies, including risk assessment, used to evaluate and control these risks will be introduced.
Human Health and the Environment in a Changing World: Read More [+]

Rules & Requirements

Prerequisites: 142 and 150A recommended. May be taken concurrently

Credit Restrictions: Students will receive no credit for PB HLTH𧆖B after completing BEHS 160, PB HLTH 150, or PB HLTH N150B. A deficient grade in PB HLTH𧆖B may be removed by taking PB HLTH 150, or PB HLTH N150B.

Hours & Format

Fall and/or spring: 15 weeks - 3 hours of lecture and 1 hour of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructors: Bradman, Cardenas

Formerly known as: second half of 150

PB HLTH𧆖D Introduction to Health Policy and Management 3 Units

Terms offered: Fall 2021, Summer 2021 First 6 Week Session, Fall 2020
This course is intended to introduce students to health policy making and health care organizations in the United States. Students will be introduced to concepts from public policy, economics, organizational behavior, and political science. Students will also be introduced to current issues in U.S. health policy and the present organization of the U.S. health care system.
Introduction to Health Policy and Management: Read More [+]

Hours & Format

Fall and/or spring: 15 weeks - 3 hours of lecture and 1 hour of discussion per week

Summer:
6 weeks - 8 hours of lecture and 2 hours of discussion per week
8 weeks - 6 hours of lecture and 2 hours of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructor: Flagg

PB HLTH𧆖E Introduction to Community Health and Human Development 3 Units

Terms offered: Spring 2021, Spring 2020, Spring 2019
This course will consist of a survey of the major social, cultural, and bio-behavioral patterns of health and well-being among individuals, families, neighborhoods, and communities. The course also will address the design, implementation, and evaluation of leading social and behavioral interventions and social policies designed to improve community and population health. This course will satisfy one of the core requirements for the undergraduate major in public health.
Introduction to Community Health and Human Development: Read More [+]

Rules & Requirements

Prerequisites: Third or fourth undergraduate standing or consent of instructor

Requirements this course satisfies: Satisfies the American Cultures requirement

Hours & Format

Fall and/or spring: 15 weeks - 3 hours of lecture and 1 hour of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Final exam required.

Instructor: Satariano

PB HLTH N150B Human Health and the Environment in a Changing World 3 Units

Terms offered: Summer 2021 First 6 Week Session, Summer 2020 First 6 Week Session
The course will present the major human and natural activities that lead to release of hazardous materials into the environment as well as the causal links between chemical, physical, and biological hazards in the environment and their impact on human health. The basic principles of toxicology, microbial ecology, GIS, exposure assessment and risk assessment among others, are covered. The overall role of environmental risks in the pattern of human disease, both nationally and internationally, are covered. The policy strategies, used to evaluate and control these risks are discussed.
Human Health and the Environment in a Changing World: Read More [+]

Objectives & Outcomes

Student Learning Outcomes: 1.
Ability to describe the basic model of environmental health.
2.
Ability to demonstrate an understanding of environmental health sciences (EHS) core areas: toxicology, microbial ecology, GIS, exposure assessment, risk assessment and environmental epidemiology at a basic level.
3.
Demonstration of oral and written communication skills in the context of environmental health sciences.
4.
Ability to describe methods used to mitigate or control adverse health impacts from environmental hazards.
5.
Demonstrate proficiency in finding primary literature sources in search engines such PubMed and WebofScience and manage citations using Zotero or equivalent software.

Rules & Requirements

Credit Restrictions: Students will receive no credit for PB HLTH N150B after completing PB HLTH𧆖B, or PB HLTH 150. A deficient grade in PB HLTH N150B may be removed by taking PB HLTH𧆖B, or PB HLTH 150.

Hours & Format

Summer: 6 weeks - 8 hours of lecture and 1 hour of discussion per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Alternative to final exam.

Instructor: Smith

PB HLTH𧆛A Senior Research Seminar in Public Health 3 Units

Terms offered: Fall 2021, Fall 2020
This applied course will help students understand how to conduct and interpret research in human health and disease, building on knowledge of epidemiology and biostatistics. The course will provide skills in: critically reading the literature related to public-health-related research, developing a research question and a testable hypothesis creating an analysis plan, applied statistical analysis of epidemiologic data, developing a research protocol for human subjects research, and case-based approaches to health issues.
Senior Research Seminar in Public Health: Read More [+]

Objectives & Outcomes

Course Objectives: 1.
Develop and define a research question.
10.
Conduct case-based analysis in areas of public health and medicine.
2.
Be proficient in finding primary literature sources and managing literature citations using bibliographic management software (such as EndNote, RefWorks, or Zoltero).
3.
Be able to critically interpret information from peer reviewed medical, public health or social science literature.
4.
Know basic data management skills and have working knowledge of R.
5.
Know how to appropriately visualize data & select appropriate statistical tests.
6.
Be able to execute & interpret basic statistical tests in R (bivariate, non-regression).
7.
Be able to execute & interpret regression analyses in R (bivariate & multivariate).
8.
Develop a research protocol and consent form for study of human subjects.
9.
Be familiar with laboratory, analytic, survey/questionnaire and other methods used in human research.

Student Learning Outcomes: LEARN: Laboratory, analytic, survey/questionnaire and other methods used in human research.
SKILLS: Be able to critically interpret information from peer reviewed medical, public health or social science literature.
SKILLS: Be proficient in finding primary literature sources and managing literature citations using bibliographic management software (such as EndNote, RefWorks, or Zoltero).
SKILLS: Develop a research protocol for study of human subjects.
SKILLS: Develop and define a research question/write Specific Aims.
SKILLS: Learn basic data management skills and have working knowledge of R software in research.

Rules & Requirements

Prerequisites: Completion of PH 142 and PH 150A (or approval from instructors). Note, it is expected that capstone students will be 4th year graduating seniors, unless otherwise given permission to enroll by the course instructors. It is expected that capstone students will have no more than two Public Health Major core course to complete at time of enrollment

Repeat rules: Course may be repeated for credit with instructor consent.

Hours & Format

Fall and/or spring: 15 weeks - 2 hours of lecture per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Alternate method of final assessment during regularly scheduled final exam group (e.g., presentation, final project, etc.).

Instructors: Barcellos, Madsen

PB HLTH𧆛B Women's Global Health and Empowerment 2 - 3 Units

Terms offered: Summer 2021 Second 6 Week Session, Summer 2020 Second 6 Week Session
The course will provide core knowledge and skills from several disciplines on how to improve women's health and well-being globally. It aims to expand students’ understanding of the interconnected factors that influence women’s health and empowerment - including foundations of sexual and reproductive health, economic development, political frameworks and global reproductive rights, demographic and social changes , basic principles of empowerment theory, educational opportunities, and advances in gender equality.
The sessions follow a life course framework, and will be taught in a seminar style with plenty of opportunities for group discussions and case studies.

Women's Global Health and Empowerment: Read More [+]

Objectives & Outcomes

Student Learning Outcomes: 1.
Identify and analyze gender inequities in health care needs and access to care.
10.
Analyze the contrasting perspectives and changing paradigms among epidemiologists, public health experts, demographers, economists, human rights activists and development specialists related to women’s health and empowerment.
11.
Explain the major theories of gender, sexuality and power.
12.
Demonstrate foundational knowledge of female anatomy, physiology and health conditions when discussing broader issues of women’s health and empowerment.
2.
Explain the ways in which social, economic, and cultural factors can both promote and impede women’s and girls’ health.
3.
Examine how girls’ education contributes to individual, community, and national development.
4.
Critically examine how gender and women’s empowerment is addressed in the Sustainable Development Goals and other development frameworks.
5.
Evaluate case studies of interventions designed to improve women’s health and empowerment in differing cultural and national contexts and recommend improvements.
6.
Compare macro level political, institutional, and structural factors that differentially influence men’s and women’s health and empowerment in relation to local, cultural, and regional contexts.
7.
Identify the major institutions and non-governmental organizations that influence women’s health and empowerment and suitable approaches for implementing interventions to ensure gender equity.
8.
Assess the impact of women’s health on advances in other sectors including child health, education, economic development, and social stability.
9.
Analyze case studies applying the relevant historical context of politics, policies, and laws related to women’s health and human rights.

Hours & Format

Summer: 6 weeks - 6-6 hours of lecture per week

Additional Details

Subject/Course Level: Public Health/Undergraduate

Grading/Final exam status: Letter grade. Alternate method of final assessment during regularly scheduled final exam group (e.g., presentation, final project, etc.).

Instructors: Hemmerling, Decker, Dunning

PB HLTH𧆛C War and Public Health 3 Units

Terms offered: Summer 2021 First 6 Week Session
Course covers global Public Health effects of war in context of war's destruction of the health care infrastructure within the Social Ecological framework. Topics include war’s impact on infectious disease & as barrier to control of vaccine-preventable diseases maternal child health health of those displaced psychosocial toll & environmental health consequences. Curriculum focuses on ongoing global conflicts & ramifications of U.S. wars in Iraq and Afghanistan, includes modules focusing on public health prevention approach to war & research methods for studying health outcomes in conflict zones. Students work in teams & apply the course material to a specific war that they will follow. Panel discussions to feature veterans & refugees.
War and Public Health: Read More [+]

Objectives & Outcomes

Course Objectives: The course will provide students with a foundation on which they can build their own line of future inquiry exploring how war impacts public health.
The objectives of this course include providing students a new paradigm through which they can identify the sustained impact of armed conflict on communities, families and individuals, and understand that those effects linger long after the dead are buried or buildings are reconstructed.

Student Learning Outcomes: Finally, they will be able to evaluate how public health’s prevention approach can be applied to armed conflict.
In addition, students should be able to place the public health effects of war within the Social Ecological framework.
Moreover, upon completion of the course, students should be able to explain the effects of war on environmental health, nutrition and psychological health.
Students should also be able to explain how war can prevent control of infectious diseases, has contributed to outbreaks or re-emergence of diseases that were previously eliminated, and has prevented the eradication of vaccine preventable diseases.
Students who take the course will apply critical thought to media reports about community violence or adverse health and place them in the framework of the public health consequences of war.
The learning outcomes of the course include the ability to explain how war’s destruction of the health care infrastructure impedes Public Health’s mission globally — particularly in war zones in low-resource countries — and how war has also impacted Public Health in US communities.


Enhancing Vitality for Successful Aging

To what extent are the effects of biological and psychological aging the inevitable results of chronological aging? Gerontologists are still trying to understand what causes these effects, and their explanations center on such things as a declining immune system, the slowing of cellular replication, and other processes that need not concern us here.

Some recent research has focused on centenarians—people at least 100 years of age—to try to find out what enables them to live so long. There are about 85,000 centenarians in the United States, and this number is expected to reach 580,000 by 2040 (Mozes, 2008). They tend to be as healthy as people in their early 80s, and their medical expenses are lower. Some eat red meat and some are vegetarians, and some exercise a lot while others exercise little. Scientists think they may have “supergenes” that protect them from cancer or Alzheimer’s disease and are trying to find these genes. The relative health of the centenarians led one researcher to observe, “Now that we know that a substantial number of people can remain robust and healthy through their 90s, at least, that should change our attitude about old age. It is no longer a curse, but an opportunity” (Hilts, 1999, p. D7).

We do not all have supergenes and we will not all become centenarians, but research shows we can still take several steps to help us age better, because what we do as we enter our older years matters much more than genetics (Centers for Disease Control and Prevention & The Merck Company Foundation, 2007). To the extent this is true, the effects of biological and psychological aging are not necessarily inevitable, and “successful aging” is possible (Evans, 2009). The steps highlighted in the gerontological literature are by now almost a cliché, but regular exercise, good nutrition, and stress reduction stand at the top of most gerontologists’ recommendations for continued vitality in later life. In fact, Americans live about 10 years less than an average set of genes should let them live because they do not exercise enough and because they eat inadequate diets (Perls & Silver, 1999).

Research by social gerontologists suggests at least two additional steps older people can take if they want “successful aging.” The first is involvement in informal, personal networks of friends, neighbors, and relatives. The importance of such networks is one of the most thoroughly documented in the social gerontological literature (Binstock & George, 2006 Adams & Blieszner, 1995) (see the “Sociology Making a Difference” box). Networks enhance successful aging for at least two reasons. First, they provide practical support, such as help buying groceries and visiting the doctor, to the elderly who need it. Second, they help older people maintain their self-esteem, meet their desire for friendships, and satisfy other emotional needs and thereby enhance their psychological well-being.

A second step for successful aging suggested by scholarly research is religious involvement (Barkan & Greenwood, 2003 Moberg, 2008). Religious involvement enhances psychological well-being among older adults for at least two reasons. As people worship in a congregation, they interact with other congregants and, as just noted, enhance their social support networks. Moreover, as they practice their religious faith, they reduce their stress and can cope better with personal troubles. For both these reasons, attendance at religious services and the practice of prayer are thought to enhance psychological well-being among the elderly. Some elders cannot attend religious services regularly because they have health problems or are no longer able to drive a car. But prayer and other private devotional activities remain significant for many of them. To the extent that religion makes a difference for elders’ well-being, health-care facilities and congregations should do what they can to enable older adults to attend religious services and to otherwise practice their religious faith.

Sociology Making a Difference

Friendships and Successful Aging

Building on the insights of Émile Durkheim, a founder of sociology discussed in Chapter 1 “Sociology and the Sociological Perspective”, sociologists have long emphasized the importance of social networks for social stability and individual well-being.

As the text discusses, social networks improve the lives of older Americans by providing both practical and emotional support. Early research on social networks and aging focused more on relatives than on friends (Roscow, 1967). Rebecca G. Adams, former president of the Southern Sociological Society, was one of the first sociologists to emphasize the role that friends can also play in the lives of the elderly. She interviewed 70 older women who lived in a Chicago suburb and asked them many questions about the extent and quality of their friendships (Adams, 1986).

In one of her most important findings, Adams discovered that the women reported receiving more help from friends than other researchers had assumed was the case. The women were somewhat reluctant to ask friends for help but did so when family members were not available and when they would not overly inconvenience the friends whom they asked for help. Adams also found that “secondary” friendships—those involving friends that a woman spent time with but with whom she was not especially close—were more likely than “primary” friendships (very close friendships) to contribute to her interviewees’ psychological well-being, as these friendships enabled the women to meet new people, to become involved in new activities, and thus to be engaged with the larger society. This finding led Adams (1986) to conclude that one should not underestimate how important friends are to older people, particularly to the elderly without family. Friends are an important source of companionship and possibly a more important source of service support than most of the current literature suggests.

Adams also asked the women about their friendships with men (Adams, 1985). The 70 women she interviewed reported 670 friendships, of which only 3.6% were with men. (About 91% were with other women, and 6% were with couples.) Although prior research had assumed that the number of these friendships is small because there are so few unmarried elderly men compared to the number of unmarried elderly women, Adams discovered from her interviews some additional reasons. Her respondents interpreted any friendship with a man as a courting or romantic friendship, which they thought would be viewed negatively by their children and by their peers. Adopting a traditional gender-role orientation, they also expected any man they might marry to be able to protect them physically and financially. Yet they also realized that any elderly man they might know would be very likely unable to do so. For all of these reasons, they shied away from friendships with men.

Work by Adams and other sociologists on the friendships and other aspects of the social support systems for older Americans has contributed greatly to our understanding of the components of successful aging. It points to the need for programs and other activities to make it easier for the elderly to develop and maintain friendships with both sexes to improve their ability to meet both their practical and emotional needs. In this manner, sociology is again making a difference.

Key Takeaways

  • Certain biological, cognitive, and psychological changes occur as people age. These changes reinforce the negative view of the elderly, but this view nonetheless reflects stereotypes and myths about aging and the elderly.
  • Regular exercise, good nutrition, stress reduction, involvement in personal networks, and religious involvement all enhance successful aging.

For Your Review

  1. Do you think the negative view of older people that is often found in our society is an unfair stereotype, or do you think there is actually some truth to this stereotype? Explain your answer.
  2. Referring back to Chapter 1 “Sociology and the Sociological Perspective”’s discussion of Émile Durkheim, how does research that documents the importance of personal networks for successful aging reflect Durkheim’s insights?

Molecular Tools and Infectious Disease Epidemiology

Molecular Tools and Infectious Disease Epidemiology examines the opportunities and methodologic challenges in the application of modern molecular genetic and biologic techniques to infectious disease epidemiology.

The application of these techniques dramatically improves the measurement of disease and putative risk factors, increasing our ability to detect and track outbreaks, identify risk factors and detect new infectious agents. However, integration of these techniques into epidemiologic studies also poses new challenges in the design, conduct, and analysis. This book presents the key points of consideration when integrating molecular biology and epidemiology discusses how using molecular tools in epidemiologic research affects program design and conduct considers the ethical concerns that arise in molecular epidemiologic studies and provides a context for understanding and interpreting scientific literature as a foundation for subsequent practical experience in the laboratory and in the field.

The book is recommended for graduate and advanced undergraduate students studying infectious disease epidemiology and molecular epidemiology and for the epidemiologist wishing to integrate molecular techniques into his or her studies.

Molecular Tools and Infectious Disease Epidemiology examines the opportunities and methodologic challenges in the application of modern molecular genetic and biologic techniques to infectious disease epidemiology.

The application of these techniques dramatically improves the measurement of disease and putative risk factors, increasing our ability to detect and track outbreaks, identify risk factors and detect new infectious agents. However, integration of these techniques into epidemiologic studies also poses new challenges in the design, conduct, and analysis. This book presents the key points of consideration when integrating molecular biology and epidemiology discusses how using molecular tools in epidemiologic research affects program design and conduct considers the ethical concerns that arise in molecular epidemiologic studies and provides a context for understanding and interpreting scientific literature as a foundation for subsequent practical experience in the laboratory and in the field.

The book is recommended for graduate and advanced undergraduate students studying infectious disease epidemiology and molecular epidemiology and for the epidemiologist wishing to integrate molecular techniques into his or her studies.


Epidemiologists

In the Air Force: Biomedical Laboratory Biomedical Laboratory, Blood Bank Biomedical Laboratory, Hematology Health Services Administrator Pathologist Pathologist, Forensic Pathologist, Neuropathology Pathologist, Pediatrics Public Health Public Health Helper Public Health Superintendent

In the Army: Biochemistry Clinical Laboratory Entomology Infectious Disease Officer Microbiology Pathologist Preventive Medicine Officer Preventive Medicine Specialist

  • Oversee public health programs, including statistical analysis, health care planning, surveillance systems, and public health improvement.
  • Plan and direct studies to investigate human or animal disease, preventive methods, and treatments for disease.
  • Provide expertise in the design, management and evaluation of study protocols and health status questionnaires, sample selection, and analysis.

Contents

The SIR model [6] [7] [8] [9] is one of the simplest compartmental models, and many models are derivatives of this basic form. The model consists of three compartments:-

S: The number of susceptible individuals. When a susceptible and an infectious individual come into "infectious contact", the susceptible individual contracts the disease and transitions to the infectious compartment. I: The number of infectious individuals. These are individuals who have been infected and are capable of infecting susceptible individuals. R for the number of removed (and immune) or deceased individuals. These are individuals who have been infected and have either recovered from the disease and entered the removed compartment, or died. It is assumed that the number of deaths is negligible with respect to the total population. This compartment may also be called "recovered" or "resistant".

This model is reasonably predictive [10] for infectious diseases that are transmitted from human to human, and where recovery confers lasting resistance, such as measles, mumps and rubella.

These variables (S, I, and R) represent the number of people in each compartment at a particular time. To represent that the number of susceptible, infectious and removed individuals may vary over time (even if the total population size remains constant), we make the precise numbers a function of t (time): S(t), I(t) and R(t). For a specific disease in a specific population, these functions may be worked out in order to predict possible outbreaks and bring them under control. [10]

As implied by the variable function of t, the model is dynamic in that the numbers in each compartment may fluctuate over time. The importance of this dynamic aspect is most obvious in an endemic disease with a short infectious period, such as measles in the UK prior to the introduction of a vaccine in 1968. Such diseases tend to occur in cycles of outbreaks due to the variation in number of susceptibles (S(t)) over time. During an epidemic, the number of susceptible individuals falls rapidly as more of them are infected and thus enter the infectious and removed compartments. The disease cannot break out again until the number of susceptibles has built back up, e.g. as a result of offspring being born into the susceptible compartment.

Each member of the population typically progresses from susceptible to infectious to recovered. This can be shown as a flow diagram in which the boxes represent the different compartments and the arrows the transition between compartments, i.e.

Transition rates Edit

For the full specification of the model, the arrows should be labeled with the transition rates between compartments. Between S and I, the transition rate is assumed to be d(S/N)/dt = -βSI/N 2 , where N is the total population, β is the average number of contacts per person per time, multiplied by the probability of disease transmission in a contact between a susceptible and an infectious subject, and SI/N 2 is the fraction of those contacts between an infectious and susceptible individual which result in the susceptible person becoming infected. (This is mathematically similar to the law of mass action in chemistry in which random collisions between molecules result in a chemical reaction and the fractional rate is proportional to the concentration of the two reactants).

Between I and R, the transition rate is assumed to be proportional to the number of infectious individuals which is γI. This is equivalent to assuming that the probability of an infectious individual recovering in any time interval dt is simply γdt. If an individual is infectious for an average time period D, then γ = 1/D. This is also equivalent to the assumption that the length of time spent by an individual in the infectious state is a random variable with an exponential distribution. The "classical" SIR model may be modified by using more complex and realistic distributions for the I-R transition rate (e.g. the Erlang distribution [11] ).

For the special case in which there is no removal from the infectious compartment (γ=0), the SIR model reduces to a very simple SI model, which has a logistic solution, in which every individual eventually becomes infected.

The SIR model without vital dynamics Edit

The dynamics of an epidemic, for example, the flu, are often much faster than the dynamics of birth and death, therefore, birth and death are often omitted in simple compartmental models. The SIR system without so-called vital dynamics (birth and death, sometimes called demography) described above can be expressed by the following set of ordinary differential equations: [7] [12]

This model was for the first time proposed by William Ogilvy Kermack and Anderson Gray McKendrick as a special case of what we now call Kermack–McKendrick theory, and followed work McKendrick had done with Ronald Ross.

This system is non-linear, however it is possible to derive its analytic solution in implicit form. [6] Firstly note that from:

Secondly, we note that the dynamics of the infectious class depends on the following ratio:

the so-called basic reproduction number (also called basic reproduction ratio). This ratio is derived as the expected number of new infections (these new infections are sometimes called secondary infections) from a single infection in a population where all subjects are susceptible. [13] [14] This idea can probably be more readily seen if we say that the typical time between contacts is T c = β − 1 =eta ^<-1>> , and the typical time until removal is T r = γ − 1 =gamma ^<-1>> . From here it follows that, on average, the number of contacts by an infectious individual with others before the infectious has been removed is: T r / T c . /T_.>

By dividing the first differential equation by the third, separating the variables and integrating we get

(note that the infectious compartment empties in this limit). This transcendental equation has a solution in terms of the Lambert W function, [15] namely

The role of both the basic reproduction number and the initial susceptibility are extremely important. In fact, upon rewriting the equation for infectious individuals as follows:

i.e., there will be a proper epidemic outbreak with an increase of the number of the infectious (which can reach a considerable fraction of the population). On the contrary, if

i.e., independently from the initial size of the susceptible population the disease can never cause a proper epidemic outbreak. As a consequence, it is clear that both the basic reproduction number and the initial susceptibility are extremely important.

The force of infection Edit

Note that in the above model the function:

models the transition rate from the compartment of susceptible individuals to the compartment of infectious individuals, so that it is called the force of infection. However, for large classes of communicable diseases it is more realistic to consider a force of infection that does not depend on the absolute number of infectious subjects, but on their fraction (with respect to the total constant population N ):

Capasso [16] and, afterwards, other authors have proposed nonlinear forces of infection to model more realistically the contagion process.

Exact analytical solutions to the SIR model Edit

In 2014, Harko and coauthors derived an exact so-called analytical solution (involving an integral that can only be calculated numerically) to the SIR model. [6] In the case without vital dynamics setup, for S ( u ) = S ( t ) >(u)=S(t)> , etc., it corresponds to the following time parametrization

An equivalent so-called analytical solution (involving an integral that can only be calculated numerically) found by Miller [17] [18] yields

Effectively the same result can be found in the original work by Kermack and McKendrick. [4]

A highly accurate analytic approximant of the SIR model as well as exact analytic expressions for the final values S ∞ > , I ∞ > , and R ∞ > were provided by Kröger and Schlickeiser, [8] so that there is no need to perform a numerical integration to solve the SIR model, to obtain its parameters from existing data, or to predict the future dynamics of an epidemics modeled by the SIR model. The approximant involves the Lambert W function which is part of all basic data visualization software such as Microsoft Excel, MATLAB, and Mathematica.

The SIR model with vital dynamics and constant population Edit

Consider a population characterized by a death rate μ and birth rate Λ , and where a communicable disease is spreading. [7] The model with mass-action transmission is:

for which the disease-free equilibrium (DFE) is:

In this case, we can derive a basic reproduction number:

which has threshold properties. In fact, independently from biologically meaningful initial values, one can show that:


Epidemiologists

  • Oversee public health programs, including statistical analysis, health care planning, surveillance systems, and public health improvement.
  • Plan and direct studies to investigate human or animal disease, preventive methods, and treatments for disease.
  • Provide expertise in the design, management and evaluation of study protocols and health status questionnaires, sample selection, and analysis.

Contents

Epidemiology means "the study of what is upon the people". The word derived from the Greek terms epi = upon, among demos = people, district logos = study, word, discourse. It applies only to human populations. But the term is used in studies of zoological populations 'epizoology', and plant populations.

Hippocrates was the first who has looked at the relationships between disease and environmental influences. He drew the distinction between 'epidemic' and 'endemic': diseases that are 'visited upon' a population (epidemic) as contrasted with those that 'live within' a population (endemic).

The Persian physician Avicenna in the 1020s, discovered the contagious nature of tuberculosis and sexually transmitted disease. He noted the distribution of disease through water and soil. Avicenna said that bodily secretion is contaminated by foul foreign earthly bodies before being infected. He introduced the method of quarantine to limit the spread of contagious disease.

The Black Death (bubonic plague) reached Al Andalus in the 14th century. Ibn Khatima thought infectious diseases were caused by "minute bodies" which enter the human body and cause disease. Another Andalusian-Arabian physician, Ibn al-Khatib (1313–1374) in his treatise On the Plague stated how infectious disease can be transmitted through bodily contact and "through garments, vessels and earrings". Girolamo Fracastoro from Verona suggested these very small, unseeable, particles that cause disease were alive. They were able to spread by air, and multiply. They could be destroyed by fire. He refuted Galen's miasma theory (poison gas in sick people). In 1543, Fracastoro's book De contagione et contagiosis morbis suggested personal and environmental hygiene to prevent disease. The development of a sufficiently powerful microscope by Anton van Leeuwenhoek in 1675 provided visual evidence of living particles consistent with a germ theory of disease.

In 1662 John Graunt analysed the mortality rolls in London before the Great Plague. This gave statistical evidence for and against various theories of disease. Dr. John Snow investigated the causes of the 19th Century Cholera epidemics. He noticed the significantly higher death rates in two areas supplied by Southwark Water Company. He showed the Broad Street pump was the origin of the Soho epidemic, a classic example of epidemiology He used chlorine in an attempt to clean the water and had the pump handle removed. This stopped the outbreak. It was a major event in the history of public health, and the founding event of the science of epidemiology.

The term 'epidemiology' was first used in 1802 by the Spanish physician Villalba. The term is used now for the description and causation of epidemic diseases, and of disease in general. It can be used for many non-disease health-related conditions, such as high blood pressure and obesity.

In 1847 Hungarian physician Ignaz Semmelweis brought down infant mortality at a Vienna hospital by disinfection. Unfortunately, disinfection did not become widely practiced until British surgeon Joseph Lister 'discovered' antiseptics in 1865 after Louis Pasteur's work. In the early 20th century, mathematical methods were introduced into epidemiology by Ronald Ross and others. In 1954 came the results of a study led by Richard Doll. This gave very strong statistical support to the suspicion that tobacco smoking was linked to lung cancer.

There are several very key terms that epidemiologists use when discussing population health and disease outbreaks. The following, although not a comprehensive list, provides some of the key concepts that are important to understand when discussing epidemiology.

  • Cases: refers specifically to those individual who are sick with a disease/health condition or injured
  • Epidemic / Outbreak: is the occurrence of a disease among a population that is in excess (higher rate) than what is expected for that given time and place
  • Endemic: a disease or health condition that is present in the population at all times during the year
  • Pandemic: a disease that spreads across various regions also refers to global outbreaks that spreads over multiple continents
  • Cluster: refers to group of cases in a specific time and place that’s more than what’s expected
  • Population at risk: refers to those within a population who are particularly susceptible to a certain disease or health condition

It is important to note that an endemic disease or cluster can become an epidemic. An example of this would be with malaria although malaria is endemic to certain regions in South America, Africa, and South Asia, during certain years or times it can become an epidemic with higher number of cases then usual present in the population. In addition, it is also possible for epidemic or outbreak to progress and become a full fledged pandemic. [1]

Rates refers to the number of cases occurring during a specific period of time and depends on the population size at that time. Calculating disease rates helps epidemiologists to compare health issues among different populations. The general calculation for determining disease rate is to divide the number of cases or health condition by the number of population at risk during a specific period of time, and multiplying that by 100. However, disease rates can also be differentiated into two different types: prevalence rate and incidence rate.

Prevalence rate refers to the number of both old and new cases in a population during a specific time period, which is divided by the total number of cases in the population. Prevalence rates are useful when dealing with investigations relating to chronic diseases, which last for more than 3 months. On the other hand, incidence rate refers to the number of new health related conditions or cases which is divided by the population at risk. Incidence rates are important in studies involving acute diseases, where symptoms of a disease peak and subside within days or weeks and generally lasts less than 3 months.

Epidemiological studies makes use of both experimental and observational studies. Experimental studies are ones where the epidemiologist can control and manipulate different variables throughout the experiment, and usually involves a placebo treatment/group. This type of study is used when epidemiologists are trying to determine the cause of a health issue/disease or evaluating the effectiveness of a cure or interventions. Observational studies include descriptive and analytical studies descriptive studies investigates epidemiological cases with regards to TPP while analytical study investigates hypothesis regarding relationships between health issues and risk factors. While descriptive studies (TPP) answers questions of when, who, and where, analytical studies tries to answer the question of how a population is affected by a disease and why they are affected. Overall, observational studies do not manipulate any variables and often uses comparison groups for analysis this type of study is often done in an attempt to discover the links between exposure to certain risk factors and health outcomes. Some examples of observational studies include cohort studies, case-control studies, and cross-sectional studies.

  • Cohort study: participants are categorized based on exposure to disease, risk factor, or presence of a health condition and are observed over time to see if they develop symptoms of the disease
  • Case-control study: Those individuals who are identified as cases (has the disease or health condition) are compared with those who don’t have the disease/health condition
  • Cross - sectional study: provides a "one-shot" picture of a group at a certain point in time participants are selected based on a specific characteristic or because they belong to a certain population/group and are examined to see how the disease/health condition has affected their group

Investigating an outbreak is a very involved multi-step process which ranges from first establishing the existence of an outbreak to communicating the findings of the investigation with the scientific community as well as the general population. The following is a rough sequence of the process of these investigations. [1] [4] [5]

  1. Establish that there is an outbreak. Epidemiologists look at data (TPP) and surveillance studies to determine if there have been similar cases, like the one being investigated, in the past or if it is a completely new type of disease or health condition.
  2. Prepare for field work. Once an outbreak has been established, epidemiologists take preparations, arrange materials/equipment for travel to investigate the outbreak at its place of origin and other locations where it may have spread to.
  3. Verify the diagnosis. Researchers review all laboratory/clinical findings and interview patients to get a better sense of what they are dealing with and to confirm their initial diagnosis of an outbreak.
  4. Define/identify case. Epidemiologists must come up with a precise and standard definition of what a case is or what a case looks like because that will be used to determine who is a case and who isn’t.
  5. Descriptive epidemiology. Then next step here is to describe the outbreak in terms of time, person, and place (TPP).
  6. Develop a hypothesis. Epidemiologists must formulate a hypothesis about cause/risk factors of the disease, then evaluate the hypothesis and refine it as needed.
  7. Implement necessary control & preventative measures. This may include things like social distancing, wearing masks, frequently washing hands, as well as isolation and quarantine.
  8. Communicate research/investigation findings. Epidemiologists must determine which information is important and how findings will be communicated. They must also determine who the audience is that needs to know the information (is it something only health care workers need to be on the lookout for or should the general public also be made aware?)

Epidemiology is a multidisciplinary subject. Members in this field mostly includes public health care workers and scientists from related fields such as chemists, biologists, geneticists, and anthropologists. People in epidemiology may work in hospital and research settings, as well as for federal organizations such as the Centers for Disease Control and Prevention (CDC). One particular unit that may be of interest for those pursuing epidemiology is with with Epidemic Intelligence Service (EIS), a subgroup within the CDC specializing in epidemiology. Epidemic Intelligence Service officers are field workers who investigate outbreaks in the US and other countries. [6] Their work aids in understanding causes of outbreaks and quickly stopping spread of diseases from one place to another notably, they have contributed to helping during various pandemics in the past, such as with smallpox, polio, and Ebola. [7]

Medical Anthropology & Epidemiology Edit

One particular field that has had an impact in epidemiology is anthropology. In the past, cultural anthropologists have been a very helpful resource in bridging the gap between different countries/cultures and the epidemiological investigators. [1] They have helped and continues to help with the development and implementation of preventative/control measures in countries in a manner that will not conflict with societal beliefs or values, which may get in the way of treatment or stopping the spread of an outbreak.

In recent years however, medical anthropology in particular has taken on a larger role in the field of epidemiology. Medical anthropology looks at biological, social, cultural, and linguistic anthropology to understand how these factors influence health and well-being, experience and distribution of illness, as well as prevention of treatment. [8] As with cultural anthropologists, medical anthropologists have continued to aid in the development of public health policies. In particular, they have been very helpful in providing a unique perspective on public health discourse. For example, they investigate how culture affects research studies, are able to pick up on seemingly "irrelevant" yet important small details that a epidemiologist might miss, and they are able to provide qualitative data whereas epidemiology only focuses on quantitative data. [9] One main thing of importance here is that while epidemiologist has largely ignored cultural factors when looking at the causes of diseases/health conditions, medical anthropology has challenged this notion and contributed to the field by showing how culture and social factors play a big role in people's willingness to follow public health guidelines/interventions or even accept treatment for their illnesses.

Whereas the nature of epidemiological investigations may lead to a reductionist or limited point of view, medical anthropology provides a more holistic view of the problem and examines the issue from different angles to best understand and help the populations in need. Another critical contribution of medical anthropology has been with regard to critical qualitative data. [10] While epidemiology is focused mainly on quantitative data and trends in health of the population, medical anthropology provides rich source of information on understanding the population's subjective experiences and providing qualitative data explaining why a particular intervention or treatment may have failed among a particular population. Their main contributions in recent years have come from modifying and helping develop epidemiological surveys by taking into account word choice and the "social suitability" of questions, so that responses would be more accurate and thereby helping to increase the validity of the questionnaires. It has also been found that medical anthropologists have played a large role in helping locals better understand the objectives of epidemiologists and thereby helped them become more receptive of their investigations. In addition to all these, one of the major contributions of medical anthropology has come from it's ability to help explain health phenomenon and create and test hypothesis relating to such explanations, in a way that epidemiologists have been unable to due to their strict focus on quantitative data. In short, while epidemiology is good at understanding numerical patterns and biological causes for disease/health conditions, it is unable to fully explain all the factors that underlie certain diseases/health conditions, and this is a gap that medical anthropology has been able to pick up on and complement by providing rich qualitative data which looks at health and diseases from a holistic perspective.

Some notable mentions of medical anthropologists who have worked and contributed to epidemiology and public health in general include Dr. Jim Kim and Paul Farmer. Dr. Jim Kim served as the president of the World Bank while Paul Farmer is a physician and medical anthropologists who focuses on infectious diseases and treatment. Both of these men co-founded the Partners in Health (PIH) program, which provided free health care to the poorest populations in countries like Haiti, Peru, and Rwanda. [1] Other notable mentions are Amber Wutich and Alexandra Brewis, both of whom are professors and researchers at Arizona State University. They focus on health impacts caused by resource scarcity, specifically relating to lack of access to clean water in developing countries. Wutich is a director of the Global Ethnohydrology study which looks at water knowledge and management in ten countries, while Brewis researches the impact of culture on human biology.

Epidemiological practice and the results of epidemiological analysis make a significant contribution to health management

  • Assess the health states and needs of a target population
  • Implement and evaluate interventions
  • Provide care for members of that population

Modern population-based health management is complex. Epidemiological practice and analysis is a core component. This task requires the forward looking ability to guide how a health system responds to current health issues, and how a health system can respond to future potential population health issues.


Watch the video: Introduction to Epidemiology: History, Terminology u0026 Studies. Lecturio (May 2022).