Epidemic is an outbreak of disease that attacks many people at about the same time. An epidemic may last a few hours, a few weeks, or many years. When a disease exists permanently in a region, it is said to be endemic. A disease that spreads throughout the world is pandemic. The term epidemic traditionally has been used to describe outbreaks of infectious diseases, such as measles, cholera, and influenza. People now often use the term to describe increased incidences of such noninfectious diseases as lung cancer or heart disease. Scientists called epidemiologists study epidemics to understand their causes and to stop epidemics from spreading.
Methods of preventing epidemics can sometimes be found before the cause of the disease is known. For example, in the 1850’s, English physician John Snow found that many Londoners with cholera obtained their water from a certain pump. He concluded that the water from the pump somehow caused the cholera. When officials closed down the pump, the incidence of cholera dropped. The bacterium that causes cholera, however, was not identified until the 1880’s. Researchers studying AIDS in the early 1980’s determined that the disease spread through sexual intercourse, through direct contact with infected blood, and from a pregnant woman to her fetus. Thus, even though HIV, the virus that causes AIDS, had not yet been identified, epidemiologists were able to recommend methods of AIDS prevention, such as the use of condoms during sexual intercourse.
Public health agencies are responsible for the control of epidemics. Immunizations can prevent epidemics of some infectious diseases, such as measles. Other epidemics are prevented by maintaining clean food and water supplies, or by controlling insects and other animals that spread disease. Informing people about the causes of epidemics and methods of prevention is crucial in the control of epidemics.
