[9] A 2003 study by Ling Zhou et al. specifically addresses these issues and clearly identifies the pathogen in this outbreak as C.
[10] 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.
[8] 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.
[8] It was also thought that melting ice and snowmelt carrying Cryptosporidium may have entered the water treatment plants through Lake Michigan.
[11] Mac Kenzie et al.[8] and the CDC[citation needed] showed that this outbreak was caused by Cryptosporidium oocysts that passed through the filtration system of one of the city's water-treatment plants, arising from a sewage treatment plant's outlet two miles upstream[citation needed] in Lake Michigan.
The increased turbidity of the treated water was mitigated by the added flocculant polyaluminum chloride, but peaked again on April 5 after the plant changed to alum three days prior.
[8] Over the span of approximately two weeks, 403,000[12] 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.