There are fewer than 5,000 epidemiologists working in the United States. Job growth statistics indicate the field will grow by approximately 15% over the next ten year period. This is faster than the average rate of growth for all jobs. This is due in part to the increasingly grim threat of bioterrorism. Outbreaks of new and serious infectious diseases such as swine flu or West Nile virus also contribute to the demand for applied epidemiologists. Research epidemiologists will face greater competition in their job searches than will applied epidemiologists.
Epidemiologists study a disease to discover the causes as well as how it spreads. With this information, they, or other researchers, can make inroads into developing a way to limit or even prevent the disease in the future.
State health departments and agencies employ applied epidemiologists who take action to get controls in place to limit the spread when serious infectious disease breaks out, especially among populations such as the elderly, newborns, or those with depressed autoimmune systems.

Clinical epidemiologists act as hospital consultants, delivering information to staff regarding outbreaks of infectious diseases and offering possible means of containment. In some cases clinical epidemiologists may also be physicians. Those who are not often partner with physicians in order to develop possible containment systems. Some clinical epidemiologists focus their efforts on developing guidelines and standards to control and treat contagious diseases.

Research epidemiologists study contagious diseases and parasite infestations that spread serious illness through contaminated food or water in an effort to repress future outbreaks or eliminate the disease entirely. Research epidemiologists will also study the parasitic life cycle in order to discover ways to interrupt it. Some focus on diseases that affect specific organs while others look at illnesses that manifest in a number of ways throughout the body, such as AIDS. They may work at colleges, medical schools, schools of public health, or independent research firms. Some teach in postsecondary programs.

Some epidemiologists are responsible for supervising public health programs. Among their specific tasks are health care planning, statistical analysis, public health improvement, and establishing surveillance systems. Others consult with state or federal departments of health, physicians, industry personnel, educators, and others who may have useful information or require it.

Risk factors for this kind of work include exposure to serious contagions. Epidemiologists must be extremely detail oriented, work well as a member of a team, and be excellent communicators as they give and receive information that could be the difference between life and death for a large population. Work environments for research epidemiologists are typically well-lit and organized, whether they work in a college, in a government labor for private industry, in hospitals or for nonprofit medical research organizations. Often, an epidemiologist will gain funding for a project by writing a grant proposal. The National Institutes of Health and the National Science Foundation, in addition to other funding organizations, provide support for projects. Those who depend upon grant approval may work under a high degree of stress due to the specific requirements of a grant and to meeting a deadline. While many epidemiologists work traditional work week hours, some will frequently work overtime.
Employers favor applied epidemiologists who have graduated from an accredited two-year master’s program in public health. A doctoral or medical degree may be required for certain types of research. Those employed by health care facilities or hospitals may need a medical degree together with focused instruction in a specific area of infectious diseases. While licensing is not always required, many employers hiring research epidemiologists may require both licensing and a medical degree if they will run clinical trials for which drugs will be administered. Undergraduate students interested in pursuing a career in epidemiology will be more likely to be accepted into a program if they have a math, chemistry and computer science background as well as biology. Some graduate students in epidemiology specialize in environmental or occupational epidemiology, surveillance methodology, infection processes or controls, or outbreak investigation.

Career advancement can take a number of forms. Some epidemiologists return to school for a medical degree; others return to specialize in a particular branch of epidemiology. Those with considerable experienced might head a research project; others might turn to teaching in a postsecondary school.
The median annual income paid to epidemiologists is approximately $62,000.