Objective: To determine risk factors for infection during a cryptosporidiosis outbreak in a rural Missouri community.
Design: Community-based case-control study.
Setting: Madison County, Missouri.
Participants: Case patients had laboratory-confirmed Cryptosporidium infection. Controls were randomly selected from the community.
Interventions: Pool water and municipal tap water were analyzed for Cryptosporidium oocysts. Univariate and multivariable logistic regression analyses were performed to evaluate potential risk factors.
Outcome measures: Risk factors for cryptosporidiosis infection.
Results: In total, 56 case patients (median age, 7.0 years) who developed cryptosporidiosis from July 27 to August 30, 2005, and 76 controls (median age, 8.4 years) participated in this study. The main risk factors for cryptosporidiosis were attending child care center A or B (adjusted odds ratio, 42.11; 95% confidence interval, 4.88-363.57) and using a water park (adjusted odds ratio, 6.02; 95% confidence interval, 1.25-29.01). A pool-based case-control study indicated that the highest risk for infection was associated with eating at the pool (adjusted odds ratio, 7.26; 95% confidence interval, 2.57-20.48). The epidemiologic curve for cases without child care exposure peaked 4 days later than that for the child care-associated cases. Samples of water from the city water plant and the water park tested negative for Cryptosporidium oocysts.
Conclusions: Children attending child care center A or B were the likely sources of this cryptosporidiosis outbreak. Recreational pool water probably served as a vehicle for disease transmission in the community. Early recognition of first cases of cryptosporidiosis by health care providers (ie, pediatricians and family physicians) caring for children could play an important role in limiting community outbreaks.