193763 An outbreak of swimming pool-associated cryptosporidiosis: How applied epidemiology influenced environmental health policy

Monday, November 9, 2009: 2:32 PM

W. David Selvage, MHS, PA-C , Infectious Disease Epidemiology Bureau, New Mexico Department of Health, Santa Fe, NM
Judy Espinoza, MPH , Environmental Health Department, City of Albuquerque, Albuquerque, NM
Raj Solomon, PE , Environmental Health Bureau, Pool Program, New Mexico Environment Department, Albuquerque, NM
Sarah L. Lathrop, DVM, PhD , Office of the Medical Investigator/Dept. of Pathology, University of New Mexico, Albuquerque, NM
Background: Cryptosporidiosis is a gastrointestinal illness caused by chlorine-resistant protozoa from the genus Cryptosporidium commonly transmitted through ingestion of contaminated recreational water. In August 2008, the New Mexico Department of Health (NMDOH) identified a cryptosporidiosis outbreak associated with a city pool in Albuquerque. The index case was a competitive swimmer who practiced and competed despite protracted diarrheal illness.

Methods: All suspected and confirmed cases were questioned with a standardized questionnaire to identify pool exposures. Confirmed and probable case definitions were developed. Water samples from the index pool were obtained. Educational posters were designed and posted at pools. A follow-up swimming behavior survey of cases was completed. Targeted messages, education and policies directed at competitive swimmers, coaches, lifeguards, pool operators and the public were developed.

Results: Overall, 92 confirmed and probable outbreak cases were identified and linked to 25 pools in the area. Thirteen competitive swimmers, swim coaches and/or lifeguards developed cryptosporidiosis. The index pool tested positive for Cryptosporidium hominis. All linked pools were closed and hyperchlorinated. The minimum chlorine threshold for city operated pools was raised from 0.4 ppm to 1.0 ppm after the outbreak.

Conclusions: Survey results suggest that competitive swimmers and lifeguards are hesitant to stop swimming when ill. Local environmental health agencies are now working with state government to ensure that required chlorination levels are maintained at all public pools. Following this outbreak, adoption of new statewide remediation policies for hyperchlorination of pools potentially contaminated with cryptosporidium were adopted and implemented.

Learning Objectives:
1. Describe the natural history of cryptosporidiosis. 2. Describe why Cryptosporidium spp. are resistant to chlorine. 3. Discuss the environmental control measures involved in curtailing and preventing swimming pool-associated outbreaks of cryptosporidiosis. 4. Discuss why swimmers continue to swim while ill with diarrhea based on responses to New Mexico's retrospective, web-based cryptosporidiosis outbreak survey.

Keywords: Infectious Diseases, Water

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: Currently I serve as the Principal Investigator for New Mexico's Emerging Infections Program FoodNet, conducting active, population-based surveillance for foodborne illnesses. I am an Associate Professor of Pathology at the University of New Mexico Health Sciences Center, and have published numerous epidemiological studies in a variety of peer-reviewed publications over the past 10 years. I work closely with David Selvage and other New Mexico Department of Health epidemiologists to analyze data related to foodborne and waterborne illnesses in our state.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.