Infectious Disease

Acute gastroenteritis outbreak at national park highlights need for prevention education

December 06, 2022

2 min read

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Disclosures:
The authors report no relevant financial disclosures.

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The largest outbreak of acute gastroenteritis recorded in the Grand Canyon National Park backcountry occurred from April to June 2022 and affected at least 222 backpackers and rafters, data in Morbidity and Mortality Weekly Report showed.

Preliminary analyzes suggested norovirus — which spreads quickly through person-to-person contact — was the cause of illness.

“If your patients are avid hikers, backpackers, rafters or general outdoor enthusiasts, help them understand how to prevent norovirus by practicing good hand hygiene and staying home if they become sick.”  ― Ariella P. Dale, PhD

“Our findings show us that it is important to think about different types of people who might need norovirus prevention education,” study co-author Ariella P. Dale, PhD, of the CDC Epidemic Intelligence Service, and colleagues told Healio. “If your patients are avid hikers, backpackers, rafters or general outdoor enthusiasts, help them understand how to prevent norovirus by practicing good hand hygiene and staying home if they become sick. Even after feeling better, people who were sick should consider delaying an outdoor trip, as ill persons can shed virus for up to 48 hours after symptoms resolve.”

In May 2022, the National Park Service Office of Public Health and Coconino County Health and Human Services in Flagstaff, Arizona, contacted the CDC regarding an uptick in the number of acute gastroenteritis cases among visitors to Grand Canyon National Park. The agencies launched an investigation that included a review of illness report forms; an assessment of infection prevention and control practices; and a detailed survey distributed to backpackers, river rafters on private and commercially operated trips that had at least one ill person, and rafters on commercial trips with no reports of illness — all of whom visited the national park between April 1 and June 17, 2022 .

Investigators defined acute gastroenteritis as onset of diarrhea or vomiting less than 24 hours prior to the trip through 3 days after the end of the trip. The survey closed on July 8, 2022.

“We identified 222 persons who had vomiting or diarrhea while in the backcountry, which is likely an underestimate of the true impact on the rafters and backpackers in the area,” the study authors said.

Those affected by acute gastroenteritis included 136 people on commercial rafting trips, 55 on private rafting trips and 31 backpackers. Survey results further revealed 80% of respondents reported onset of illness during the trip, with 86% of cases occurring among park visitors and 14% among park guides. Visitors who reported illness came from 34 US states and four other countries.

Investigators also used real-time reverse transcription-polymerase chain reaction to test specimens from portable toilets used by river rafting groups. Pooled specimens from affected trips tested positive for norovirus.

Park staff, river outfitters and public health partners implemented norovirus prevention and control measures, including recommendations for symptom screening, disinfection of potable water, promotion of handwashing with soap and water, and exclusion of ill people from trips. The last report of acute gastroenteritis at the park was on June 17.

“Norovirus continues to be a significant cause of illness in our communities; however, it is often underreported,” the authors said. “In fact, each year norovirus causes 900 deaths, mostly among adults aged 65 and older; 109,000 hospitalizations; and 465,000 emergency department visits, mostly in young children.”

They added, “This outbreak reminds us how important practicing good hand hygiene with soap and water is, as well as staying home if you become sick is, for preventing norovirus outbreaks.”

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