What is Epidemiology?

Epidemiology is the scientific method used to investigate, analyze and prevent or control a health problem in a population. That population could be the entire world, as may be the case with an influenza epidemic. Or it can be a relatively small group of people—a single high school, for example, with an unusually high number of kids with asthma.

It may be useful to think about how epidemiology is different from the practice of medicine. If you came down with a case of food poisoning, your doctor would examine you and recommend treatment. An epidemiologist would want to know more:

What food made you ill?
Where did you get the food?
Who else might have eaten it?
What groups of people, such as children or the elderly, are most threatened by the illness?
How could people be notified and treated?
How did the food become tainted in the first place?

As you can see, epidemiologists are interested in all kinds of health issues—not just the well-known infectious diseases such as SARS or HIV/AIDS. An "epidemic" is simply a health problem that exists in a community to a greater degree than you would expect. Other examples of trends epidemiologists might look at are:

chronic illnesses, such as asthma or obesity
causes of premature death, such as youth violence or automobile accidents
factors that put people at risk for health problems, such as smoking or exposure to toxic waste
factors that keep people healthy, such as a balanced diet or regular physical activity

Epidemiologists make headlines and save lives. They're also in demand more than ever before. Diseases such as SARS travel around the globe rapidly. Bioterrorism is a very real threat. And we're finding out more every day about the role of environment and lifestyle choices in our health. Our quality of life—and even our survival—depends in large part on the work of epidemiologists.