1993 Milwaukee cryptosporidiosis outbreak

Cryptosporidium are a chlorine-resistant enteric pathogens that cause gastrointestinal illness (cryptosporidiosis) with symptoms such as diarrhea. Other symptoms include stomach cramps, dehydration, nausea, vomiting, fever, or weight loss. Since Cryptosporidium is a coccidian parasite, it has oocysts. An oocyst is a period in the life cycle of a coccidian parasite. The oocysts in Cryptosporidium are the transmissible stage for cryptosporidiosis. Most reports do not specify the species of Cryptosporidium involved in the outbreak. Several species cause cryptosporidiosis in humans, with most caused by Cryptosporidium parvum and Cryptosporidium hominis. However adding to the confusion, these two species were only split from each other in 2002. but the 1994 source they cite does not specify the species. A 2003 study by Ling Zhou et al. specifically addresses these issues and clearly identifies the pathogen in this outbreak as C. hominis. == History ==

On April 4, 1993, pharmacist Jeff Langer contacted a local television station after the Milwaukee Health Department did not respond to his calls regarding substantial increase in gastrointestinal complaints. Sunday evening, April 4, the station came out to interview Jeff Langer regarding the substantial increase in requests for anti-diarrhea medications. Following that television interview, April 5, 1993, Milwaukee Health Department received additional reports of gastrointestinal illness at their local hospitals and calls of complaints related to reduced water-quality aesthetic. Water aesthetics include taste, color, odor, hardness/softness, and turbidity. They are considered a secondary standard under the EPA National Primary Drinking Water Regulations (NPDWR). Although these drinking aesthetics are under the EPA NPDWR, they are not federally enforced but are standard regulations that states may choose to adopt and enforce themselves. In the spring of 1993, turbidity was the main complaint. This was corroborated by Milwaukee Water Works records of Maximal Turbidity for both water treatment plants from March through April 1993. == Causes ==

The root cause of the epidemic was never officially identified; however, it was most likely the result of human error at the Howard Avenue Water Treatment Plant. Initially it was suspected to be caused by runoff from upstream cattle pastures. It was also thought that melting ice and snowmelt carrying Cryptosporidium may have entered the water treatment plants through Lake Michigan. Mac Kenzie et al. 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, diarrhea and dehydration caused by the pathogen. Deaths have been attributed to this outbreak, mostly among the elderly and immunocompromised people, such as people with AIDS. == Social impact ==

Reports of gastrointestinal illness began in April 1993; however, studies occurring after the outbreak confirmed that there were echoes of the epidemic beyond initial contamination as the population contracted the illness through secondary transmission. It took ten years for Milwaukee citizens to begin to trust the public water supply again with the help of frequent community outreach by the utility. == Current treatment in Milwaukee ==

In the 2020s, Milwaukee consistently scored as one of the highest drinking water qualities in the state. This is due to $508 million invested in water treatment and monitoring improvements since the outbreak. Improvements in treatment include: • Activated charcoal filtration (Actiflo Carb) removes certain drugs, disinfectants, antibiotics • Monitoring on each stream of flow (8 streams) – previously, streams were only monitored before and after branching off (no way to monitor individual streams) • Online monitoring/automation == See also ==