Milwaukee Cryptosporidiosis outbreak

USA’s largest waterborne disease outbreak occurred in 1993 when 1/4 of Milwaukee (403,000 people) developed stomach cramps, fever, and diarrhea. The cause was found to be the Cryptosporidium protozoan. The root cause of the epidemic was never officially identified. Initially, it was suspected to be caused by the cattle genotype due to runoff from pastures.