Cryptosporidium risk from swimming pool exposures.

Area of Science:

• Environmental microbiology
• Public health
• Risk assessment

Background:

• Infection risk estimates from swimming in treated recreational water venues are lacking.
• Quantitative infection risk estimates among different age groups are needed to identify vulnerable populations.
• High-risk populations can be targeted during public health interventions.

Purpose of the Study:

• To estimate per-swim and annual Cryptosporidium infection risks in adults and children.
• To identify vulnerable populations for public health interventions.
• To assess the influence of swimmer behavior on infection risk.

Main Methods:

• Utilized oocyst concentration data from literature and new experimental data on swimmer behavior (pool water ingestion, swim duration, frequency).
• Estimated per-swim and annual Cryptosporidium infection risks.
• Conducted a sensitivity analysis to identify influential model variables.

Main Results:

• Average estimated per-swim Cryptosporidium infection risk was 2.6×10^-4 infections/swim.
• Annual infection risk was estimated at 2.9×10^-2/year for children and 2.2×10^-2/year for adults.
• Child swimmers had the highest annual risk due to increased ingestion and swim duration; Cryptosporidium concentration was the most influential variable.

Conclusions:

• Results suggest the need for standardized pool water quality monitoring for Cryptosporidium.
• Interventions to reduce ingestion and improve oocyst removal are recommended.
• Child swimmers are the most vulnerable sub-population and should be targeted in healthy swimming education campaigns.