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.