ABSTRACT
The Centers for Disease Control and the Environmental Protection Agency have conducted waterborne disease investigation and surveillance activities and have published information on waterborne outbreaks annually since 1971. An increase in reported outbreaks similar to that experienced by community and noncommunity water systems during the late 1960s through 1980 was not seen in individual water systems. In a few instances the number of cases of illness resulting from an outbreak was reported to be unknown or many, and an estimate of the number of actual illnesses was required. The magnitude of a waterborne outbreak depends upon the type of water system affected. For the entire 61-year period, community water systems averaged 559 illnesses per outbreak, noncommunity systems averaged 84 illnesses per outbreak, and individual systems averaged 22 illnesses per outbreak. An etiologic agent was determined in 56% of the waterborne outbreaks.
