Top 5 Takeaways

  1. Definition and Scope of the Outbreak: Confirmed cases were tied to specific laboratory findings from stool samples among children visiting the community pool between May 31 and June 7, 2021, with probable cases based on gastrointestinal symptoms following the visit.
  2. Malfunctioning Equipment and Inadequate Record Keeping: A malfunctioning chlorinator and poor record-keeping practices likely led to inadequate chlorine levels, facilitating the transmission of pathogens.
  3. Health Impact: The outbreak resulted in 15 cases of illness in children aged 4–14, with some requiring hospitalization. Fortunately, no cases of hemolytic uremic syndrome were reported.
  4. Importance of Appropriate Testing: C. difficile testing was determined to be incidental and unnecessary for the cases as the children were healthy and lacked risk factors typically associated with C. difficile infection.
  5. Recommendations for Prevention: Proper treatment and maintenance of recreational water settings are crucial, and individuals with diarrhea should refrain from swimming to prevent outbreaks.

Original Article Author and Citation

Corresponding Author

Molly E. Nace,

Suggested Citation

Nace ME, Wallace JL, Kline KE, Plipat N. Notes from the Field: Escherichia coli O157:H7 Outbreak in Children with Clostridioides difficile Colonization Associated with an Improperly Treated Swimming Pool — Pennsylvania, June 2021. MMWR Morb Mortal Wkly Rep 2022;71:690–691. DOI:


The outbreak involved multiple complaints of gastrointestinal illness linked to a community swimming pool in Pennsylvania. The health department defined and investigated cases based on laboratory results and symptoms reported by the pool visitors.


The investigation focused on reviewing stool sample lab reports, pool maintenance records, and interviewing affected individuals. The public health response included closing the pool, inspecting the equipment, and ensuring proper treatment before reopening.


The incident underlines the critical role of adequate facility maintenance and the need for rigorous public health surveillance to prevent similar outbreaks. The findings also emphasize the significance of appropriate diagnostic criteria and treatment guidelines in managing enteric diseases.


This event highlights the necessity of proper swimming pool treatment and public health readiness to quickly address and resolve such outbreaks. Continued education on the importance of not swimming when ill is vital for community health safety.

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