Between April 1 and June 17, 2022, at least 222 rafters and backpackers became infected with acute gastroenteritis, most likely norovirus, according to the Centers for Disease Control and Prevention (CDC). This is the largest outbreak of acute gastroenteritis documented in the Grand Canyon National Park backcountry.
Preliminary analysis of illness characteristics and portable toilet specimen test results suggested norovirus as the primary causative agent of illness. Norovirus spreads quickly through person-to-person contact and contaminated food or beverages and can persist in the environment. The bacteria can live for days to weeks on hard surfaces.
River outfitters and National Park staff members partnered to enable the implementation of prevention and control measures.
Norovirus-associated acute gastroenteritis is highly transmissible in settings with close person-to-person contact and decreased access to hand hygiene. Because many trips use the same campsites and place-portable toilets in the same locations, particles could have been transmitted to surfaces, beach sand or river water where new groups could have encountered them, and then transmitted the virus both from person-to-person and trip-to-trip.