Betsy Taylor of the Associated Press reports that the Madison County Health Department said Monday that no one source was discovered for illnesses caused by microscopic parasites that sickened dozens of people earlier this year.
Between the first reports on Aug. 8 and the last on Sept. 14, the department in Missouri received word of 57 cases of the illness, said registered nurse Carolyn Amelunke. Despite work to determine where the illness began, no starting point was identified, she said.

The Fredericktown municipal swimming pool voluntarily shut down after the first cases were identified. One of the first children with a confirmed case was at the pool, but several of those infected with the parasite had not been there. It is expected to open again next season, Amelunke said.
The majority of cases were an illness called cryptosporidiosis, though there were two reports of giardiasis, both caused by tiny parasites. Symptoms included diarrhea, nausea, headache, low-grade fever and loss of appetite.