In August 2012, two cases of Cryptosporidium parvum were identified by the Minnesota Department of Health (MDH) through routine surveillance. Interviews with the cases showed that both had been swimming at an aquatic center located in Red Wing, Minnesota. One case was hospitalized for 3 days.

By the time investigators were notified, the aquatic center had closed for the season. Review of pool records indicated there had been a vomiting accident in the aquatic center on August 1 and a fecal accident on August 6. Despite having a fecal response protocol, limited information on the chlorine concentration and the length of superchlorination time was documented.