Public health officials have determined that an outbreak of E. coli infections in a Utah city were caused by untreated municipal irrigation water.

In July through September 2023, there were 13 children confirmed with infections. Seven of the patients required hospitalization and two developed hemolytic uremic syndrome, a type of kidney failure.

The children had played in or drank water from home hoses and sprinklers before becoming ill. A report on the situation by the U.S. Centers for Disease Control and Prevention did not name the city, as is standard practice for certain of the agency’s investigations.

Public health officials recommended education about the untreated irrigation water including lines and spigots with a designated color, and providing conspicuous signage to communicate risk and intended use.

Untreated, pressurized irrigation water is surface water that is piped from reservoirs to homes. iI is intended for outdoor landscapes and is not suitable for drinking or recreational activities. untreated, pressurized, municipal irrigation water is not routinely monitored or tested.

Outbreak investigators collected samples at two reservoirs and nine sites wher persons with confirmed illness reported exposure, including private homes. In addition to water, samples of sediment and bird feces from the reservoirs; and swabs of spigots, hoses, toys, and other surfaces likely to have had contact with the water were collected.

Investigators observed birds on and around the reservoirs during the environmental investigation, but no other animals or obvious potential sources of E. coli O157:H7 were observed during sampling.

Public health officials issued a press release on Aug. 4 after identification of the first eight patients, before the environmental investigation, notifying the public of the outbreak, and warning against drinking or playing in the irrigation water. After the press release, two additional patients were reported.

On Aug. 19, the city issued a second press release, stating that E. coli O157:H7 had been detected in irrigation water samples and recommending that residents cook homegrown produce and avoid watering lawns and renewed warnings not to drink or play in the irrigation water.

The city distributed mailers on Aug. 28, further informing residents of the risks associated with using the irrigation water for drinking or recreation.

Untreated, pressurized irrigation water systems are generally uncommon in the United States, according to the CDC. However, they are used in some Utah communities to irrigate residential outdoor landscapes. These systems were designed to conserve drinking water and reduce water treatment costs. 

In 2010 and 2015, two other Utah cities experienced campylobacteriosis outbreaks that were suspected to have been caused by cross-connections between untrusted irrigation water and drinking water lines, according to the Utah Department of Health and Human Services. Data from the city’s outbreak did not specifically implicate homegrown produce as an illness-causing vehicle, but previous outbreaks demonstrated that produce grown with water containing E. coli O157:H7 can cause illness.

“This outbreak demonstrates the need for ongoing educational efforts and reminders. Educating residents of communities with (pressurized, untreated irrigation water) systems, especially those at higher risk for severe illness, including older adults, children, and persons with compromised immune systems, about the importance of using (pressurized, untrusted irrigation water) for its intended purposes as well as the risks associated with drinking and recreational exposure, could prevent future cases of waterborne illness,” according to the CDC.