The outbreak, which occurred between April 1 and June 17, was the largest outbreak of acute gastroenteritis documented in the Grand Canyon National Park backcountry, the agency said.
On May 11, National Park Service officials in Flagstaff, Arizona, first contacted the CDC about a rising number of cases among visitors. The park service said it collected specimens from portable toilets used by nine river rafting trip groups, which were positive for norovirus.
“Norovirus-associated acute gastroenteritis is highly transmissible in settings with close person-to-person contact and decreased access to hand hygiene, such as backpacking or rafting,” the CDC explains.
In response, agencies recommended regular disinfection of drinkable water spigots, promotion of proper handwashing whenever possible, and separation of people who are sick from those who aren’t.
The CDC also emphasized the need for rapid reporting of illnesses.
In the report, a case of acute gastroenteritis was defined by the CDC as vomiting or diarrhea less than 24 hours before trip launch through three days after the end of the trip during the 77-day time period.