This summer, be very afraid to go in the water: Cryptosporidium outbreaks associated with swimming pools in Maricopa County, AZ 2008

In the summer of 2008, three cryptosporidiosis outbreaks were detected in Maricopa County, Arizona. These outbreaks involved recreational water facilities in public pool systems in two cities and a children's splash area in a third city. In contrast to outbreaks recently reported elsewhere, these outbreaks were not communitywide. During the three outbreaks, 221 reports of illness were received. Maricopa County Department of Public Health (MCDPH) in partnership with a student team from the University of Arizona conducted 101 interviews. Fourteen specimens were collected and tested, with 13 confirmed and 64 probable cases. Six pools were inspected, 37 hyperchlorinated, two pools tested positive for Cryptosporidium oocysts. Stool specimens from the two public pool outbreaks yielded Cryptosporidium that were a genetic match linking the two outbreaks. Water samples from the children's pool showed a different genetic pattern.

Increases in cryptosporidiosis cases were linked to the three outbreaks investigated. One outbreak was detected by case surveillance and two were reported by the public as gastrointestinal illness complaints. In both public pool system outbreaks the majority of confirmed cases were due to MCDPH collection and testing of specimens. Cases confirmed by private lab testing occurred much later.

In 2009, MCDPH will disseminate educational information to pool operators and the public prior to the start of the pool season to help prevent cryptosporidiosis. MCDPH will pursue single cases of cryptosporidiosis associated with recreation water exposure to facilitate the early detection of outbreaks. Increases in pool inspections this summer are also planned.