Milwaukee Cryptosporidium outbreak

The 1993 Milwaukee Cryptosporidium outbreak was a significant distribution of the Cryptosporidium protozoan in Milwaukee, Wisconsin, and the largest waterborne disease outbreak in documented United States history. The Howard Avenue Water Purification Plant (see Town of Lake water tower) was contaminated, and treated water showed turbidity levels well above normal. It was one of two water treatment plants for Milwaukee. The root cause of epidemic was found to be sewage that passed through the filtration system of one of the city's drinking water plants.

This abnormal condition at the plant lasted from March 23 through April 8, after which, the plant was shut down. Over the span of approximately two weeks, 403,000 of an estimated 1.61 million residents in the Milwaukee area (of which 880,000 were served by the malfunctioning treatment plant) became ill with the stomach cramps, fever, diarrhoea and dehydration caused by the pathogen. Over 100 deaths were attributed to this outbreak, mostly among the elderly and immunocompromised people, such as AIDS patients.