BACKGROUND: Cryptosporidium is an intestinal parasite that can infect humans and animals. It is the leading cause of recreational water illness outbreaks in the United States.1 In August 2014, the DeKalb County Board of Health Division of Environmental Health (DCBOH) and Georgia Department of Public Health (GDPH) investigated an outbreak of Cryptosporidiosis at a membership-only neighborhood pool after being notified of a potential outbreak by a member.
METHODS: The investigation included environmental assessments, collection of water specimens, solicitation of clinical specimens, and interviews. DCBOH and GDPH elicited illness and exposure history using an online survey distributed via social media and email. A cohort study was performed, and survey responses were analyzed using EpiInfo7. The Georgia Public Health Laboratory and CDC tested clinical and water specimens.
RESULTS: At the initial assessment, the facility was found to be in compliance with the local ordinance. No fecal incidents had been reported; however, the facility was closed due to illness reports. Sixty-three patients met the case definition of laboratory evidence of infection and/or vomiting and/or diarrhea and/or abdominal pain since July 25th. Twelve cases (14%) tested positive for Cryptosporidium spp. by a variety of methodologies (5 PCR, 2 EIA, 5 microscopy). Cryptosporidium spp. oocysts were observed by microscopy of filter backwash from both the main and wading pools. The facility reopened after hyperchlorinating the main pool per CDC recommendations2 and draining and acid washing the wading pool. Individuals reporting any exposure to the main or wading pool between July 25 and August 9 were 2.99 (p<0.05) and 1.33 (p<0.05), respectively, times more likely to become ill compared to those with no reported exposure during the same time period. The main pool was associated with an increased risk for illness on August 2, 3, 4, 6 and 7 (RR = 1.41, 1.82, 1.44, 1.37, 1.43 respectively).
CONCLUSIONS: Exposure to the main pool was implicated through epidemiologic and laboratory evidence. Even in the absence of an observed fecal incident, this pool was contaminated with Cryptosporidium oocysts. Swimmer education by pool operators and public health is essential in preventing future outbreaks of Cryptosporidiosis.