The source of the Cryptosporidium is believed to be overflow from the Milwaukee area combined sanitary and storm sewer system into Lake Michigan, which was then taken into the Howard Avenue Water Purification Plant and distributed to an estimated 880,000 residents (of the 1.61 million residents in the Milwaukee area who receive their drinking water from Lake Michigan). These residents, who receive their drinking water from Lake Michigan, were told to boil their water before drinking it. More people were affected in this one outbreak than the combined number of people affected in every cryptosporidiosis outbreak in the 24 years since then. An estimated 69 people died during the outbreak, according to the CDC. The UKs biggest outbreak occurred in Torbay in Devon in 1995. In the summer of 1996, Cryptosporidium affected approximately 2,000 people in Cranbrook, British Columbia, Canada. Weeks later, a separate incident occurred in Kelowna, British Columbia, where 10,000 to 15,000 people got sick. 2001–2009
In April 2001, an outbreak occurred in the city of North Battleford, Saskatchewan, Canada. Between 5800 and 7100 people had diarrheal illness, and 1907 cases of cryptosporidiosis were confirmed. Equipment failures at the citys antiquated water filtration plant following maintenance were found to have caused the outbreak. In the summer of 2005, after numerous reports by patrons of gastrointestinal upset, a water park at Seneca Lake State Park, in the Finger Lakes region of upstate New York was found to have two water storage tanks infected with Cryptosporidium.
Both the modified zinc sulfate centrifugal flotation technique and the Sheathers sugar flotation procedure can concentrate the oocysts by causing them to float. Another form of microscopy is fluorescent microscopy done by staining with auramine.Other staining techniques include acid-fast staining, which will stain the oocysts red. One type of acid-fast stain is the Kinyoun stain. Giemsa staining can also be performed. Part of the small intestine can be stained with hematoxylin and eosin (H & E), which will show oocysts attached to the epithelial cells.Detecting antigens is yet another way to diagnose the disease. This can be done with direct fluorescent antibody (DFA) techniques. It can also be achieved through indirect immunofluorescence assay. Enzyme-linked immunosorbent assay (ELISA) also detects antigens.Polymerase chain reaction (PCR) is another way to diagnose cryptosporidiosis. It can even identify the specific species of Cryptosporidium. If the patient is thought to have biliary cryptosporidiosis, then an appropriate diagnostic technique is ultrasonography. If that returns normal results, the next step would be to perform endoscopic retrograde cholangiopancreatography. Prevention
Many treatment plants that take raw water from rivers, lakes, and reservoirs for public drinking water production use conventional filtration technologies. This involves a series of processes, including coagulation, flocculation, sedimentation, and filtration. Direct filtration, which is typically used to treat water with low particulate levels, includes coagulation and filtration, but not sedimentation. Other common filtration processes, including slow sand filters,  diatomaceous earth filters and membranes will remove 99% of Cryptosporidium.