By Donna Campisano, specialist, Communications, APHL

In the summer of 2023, E. coli cases started popping up in Lehi, Utah, a suburb of Salt Lake City in Utah County.

From July to September, 13 children were sickened. Seven of them were hospitalized, two with hemolytic uremic syndrome (HUS), a serious, life-threatening condition that can cause kidney failure, red blood cell destruction and blood vessel damage. The median age of the children was four years.

The culprit wasn’t undercooked hamburger meat, unwashed lettuce or improperly chlorinated pool water. The culprit, it turns out, was untreated pressurized municipal irrigation water (UPMIW), the kind that flows through hoses and sprinklers in Lehi and was used to wet backyard lawn water slides, inflatable water toys and water play tables.

The water, which is intended to irrigate gardens and lawns, is not treated, tested or routinely monitored. It is also not city or state regulated.

Testing the Waters

From July 25-30, six cases of Shiga toxin-producing E. coli O157:H7 were reported to the Utah County Health Department. Preliminary whole genome sequencing was performed on stool samples by the Utah Public Health Laboratory (UPHL).

“Two isolates were nearly identical at the DNA level, indicating that two patients were infected with the same bacteria and there was a common exposure,” said Kelly Oakeson, PhD, chief scientist for bioinformatics and next genome sequencing at UPHL, whose team performed all the sequencing of clinical samples.

And what was that common exposure? After investigators were sent to the children’s homes and parents were interviewed, they had their answer: UPMIW.

Lehi’s pressurized municipal irrigation water consists of melted mountain snow that is carried by a river to an underground pipeline and then to open reservoirs. At the reservoirs, investigators took samples of sediment, bird feces and other ruminant (i.e., deer, cattle, etc.) feces, all of which can harbor E. coli bacteria. They also swabbed outdoor spigots, hoses and water toys thought to have been exposed to UPMIW.

Samples of the bird feces were sent to UPHL while the other samples were sent to the Centers for Disease Control and Prevention (CDC). E. coli O157:H7 was isolated in sediment and water samples in the majority of exposure sites. Once again, sequencing showed that the E. coli isolates in the environmental samples were nearly identical.

Sounding the alarm

With the outbreak and its source detected, the Utah County Health Department issued three press releases and one mailer over several weeks, urging residents not to drink or play in UPMIW. They also cautioned residents against watering their lawns (E. coli can still be present even on dry grass) and eating raw fruits and vegetables that may have been exposed to UPMIW.

An account of the outbreak was published in May in Morbidity and Mortality Weekly Report.

In the report, researchers noted that the main purpose of UPMIW, which is not commonly found in the US, is to conserve water and reduce water-treatment costs. Overall, 12 of the 13 sickened children reported playing in or drinking UPMIW. Although residents are periodically warned about the dangers of consuming or playing in UPMIW, the report noted that the population has increased in the area over the years and there were likely some residents who were unaware of the hazards. To prevent future health events associated with UPMIW, the researchers suggested several mitigation efforts, including color-coding spigots and lines that use UPMIW so residents would know what’s safe to use and what’s not.

“I think an important takeaway from this is to be aware of where your food and water come from,” said Oakeson, who noted the quick detection of the E. coli outbreak and the public health response were due to a strong partnership between labs and local, state and federal agencies. “I think we take for granted that the food we eat, the water we drink and play in, and the air we breathe are all safe and won’t make us sick. However, that isn’t always the case, and we need to be more cognizant of our environment and what we eat and drink.”

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