Epidemic

Occurs when new cases of a certain disease occur in a given human population, during a given period, substantially exceed what is "expected," based on recent experience (the number of new cases in the population during a specified period of time is called the incidence rate). (An epizootic is the analogous circumstance within an animal population.) In recent usages, the disease is not required to be communicable; examples include cancer or heart disease. (EPIDEMIA).