Epidemiology is a term that refers to the techniques and analysis methods that are used to pinpoint the source of an illness. As well, epidemiologists (those who conduct the epidemiological investigations) are concerned with the distribution of the infection.

Typically, epidemiology is concerned with an illness outbreak involving the sudden appearance of a disease or other malady among a group of people. Examples of situations where epidemiology would be of use are an outbreak of food poisoning among patrons of a restaurant, or a disease outbreak in a geographically confined area.

Many illnesses of epidemiological concern are caused by microorganisms. Examples include hemorrhagic fevers such as that caused by the Ebola virus, toxic shock syndrome, Lyme disease caused by the Norwalk virus, and Acquired Immunodeficiency Syndrome caused by the Human Immunodeficiency Virus. The determination of the nature of illness outbreaks...