In August 2012, Minnesota Department of Health and City of Bloomington Environmental Health staff investigated an outbreak of Cryptosporidium parvum associated with swimming at an aquatic center in Bloomington. Six outbreak associated cases were identified. No one was hospitalized and no one died. Reported onset dates ranged from August 8 to August 17. Cryptosporidium parvum subtype BGP3 was identified in all specimens.

Nineteen aquatic center staff were interviewed about recent illness and job duties. Three reported being recently ill with vomiting and diarrhea lasting > 3 days, with reported onset dates from July 31 to August 10. Ill staff were restricted from working while ill and for 2 weeks following the resolution of symptoms.

Upon inspection, the aquatic center was found to be operating properly and was within state regulatory limits for pH and chlorine levels. However, Cryptosporidium can survive and be transmitted even in properly operated pools.

Although the original source of contamination was not identified, an infectious aquatic center user most likely introduced the parasite into the center.