Investigating the E coli Outbreak in City A, Utah

E coli is a gram-negative bacteria, part of the human intestine microbiome, escherichia coli can cause food poisoning.

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An outbreak of Escherichia coli O157:H7 illness occurred among children in City A, Utah. The outbreak resulted in 13 confirmed illnesses, with 7 patients requiring hospitalization, including 2 with hemolytic uremic syndrome. The investigation by local, state, and federal public health partners identified untreated, pressurized municipal irrigation water (UPMIW) in city A as the likely source of exposure. Recommendations include public education, UPMIW management interventions, and enhanced monitoring to prevent future outbreaks.

The investigation linked the illnesses to exposure to UPMIW, with 12 out of 13 ill children reporting playing in or drinking UPMIW. Genetic analysis revealed a high similarity between clinical and environmental isolates from various locations within city A’s UPMIW system. Microbial source tracking suggested birds and ruminants as potential sources of fecal contamination of UPMIW. Public health interventions, including public education and UPMIW management measures, were implemented to mitigate future risks.

“UPMIW systems are generally uncommon in the US; however, they are used in some Utah communities to irrigate residential outdoor landscapes,” according to the investigators. “These systems were designed to conserve drinking water and reduce water treatment costs. Utah UPMIW systems are not intended for drinking or recreation, are not monitored or tested for water quality, and, except for 2022 state legislation requiring metering, are not currently regulated by state or local authorities.”

Public health officials investigated to determine the source of the outbreak and employed methods including genetic analysis of clinical and environmental isolates to identify relatedness, as well as microbial source tracking to pinpoint potential contamination sources. Additionally, public health and city officials issued press releases to inform residents and implemented various interventions to prevent future outbreaks.

“Although UPMIW is not intended for recreation, all but one child with UPMIW exposure in this outbreak reported some kind of play in the water,” according to the investigators. “Utah water providers have previously instructed residents to not drink or play in UPMIW; however, recent population growth within city A might have resulted in residents who arrived more recently being uninformed about UPMIW-associated risks. This outbreak demonstrates the need for ongoing educational efforts and reminders.”

On August 4, UCHD issued a press release warning against drinking or playing in UPMIW after identifying 8 cases. 2 more cases were reported afterward. On August 19, city A confirmed STEC O157:H7 in UPMIW samples and advised cooking homegrown produce, avoiding lawn watering, and reiterated warnings against UPMIW use. City A mailed informational leaflets on August 28. Additionally, the Utah Department of Health and Human Services urged healthcare providers on August 22 to test stool for diarrheal illnesses, educate on HUS symptoms, and avoid antibiotic treatment for STEC infections due to HUS risk.

The investigation identified untreated UPMIW as the source of the outbreak, emphasizing the importance of public education and management interventions to prevent future incidents. Recommendations include enhanced monitoring and regulation of UPMIW systems, as well as ongoing educational efforts to inform residents about associated risks.

References

1. Osborn B, Hatfield J, Lanier W, et. al. Shiga Toxin–Producing Escherichia coli O157:H7 Illness Outbreak Associated with Untreated, Pressurized, Municipal Irrigation Water — Utah, 2023. Published May 9, 2024. Accessed May 13, 2024. https://www.cdc.gov/mmwr/volumes/73/wr/mm7318a1.htm?s_cid=mm7318a1_w