A 1993 outbreak of cryptosporidiosis in Milwaukee, Wisconsin, is the largest outbreak of waterborne disease in the United States. Lake Michigan is the source of Milwaukee s water, which is treated by filtration and disinfection. Due to an unusual combination of circumstances during a period of heavy rainfall and runoff the treatment plant was ineffective, resulting in an increase in the turbidity of the treated water. Increased turbidity can be, and was in this case, an indicator of higher levels of Cryptosporidium. The original source of contamination is uncertain.
Boiling water kills the organisms that can cause disease.
Therefore, the notices serve as a precaution for the public. Boil water notices are being issued more frequently in recent years. At least 725 other communities have also issued notices affecting almost 3 million people in the past few years. If untreated, the condition could be fatal. Radon in Water Naturally occurring contaminants also are being found in drinking water.