“At least 222 rafters and backpackers became infected, probably with norovirus,” said the agency in a recent update. “Strong partnerships with river outfitters and National Park staff members enabled implementation of prevention and control measures.”
Between April 1 and June 17, tourists reported being sick during or after their trips to the Grand Canyon, the CDC said. Of that figure, 178 people reported being sick during their visits, and at least 94 rafters reported vomiting while another 79 reported diarrhea, according to the agency.
“Specimens from portable toilets used by nine river rafting trip groups were tested … and test results were positive for norovirus,” the CDC said.
In response, an executive with the Grand Canyon River Outfitters Association said that a norovirus outbreak of that scale is highly unusual.
“For us to experience the several trips that did have norovirus, that was just unprecedented. We’ve never experienced anything to that level ever,” John Dillon, the executive director of the Grand Canyon River Outfitters Association, told local media outlet AZFamily.
And a spokesperson for the Grand Canyon park, Jan Balsom, told the Daily Beast that they “haven’t seen something like this kind of outbreak in about 10 years.”
In June, park officials said in a release that “comprehensive control measures” have been implemented in response to the outbreak. Since then, they’ve seen a “marked decrease in reports of illness,” the release said.
CDC authorities did not elaborate on a possible cause of the outbreak.
The norovirus is a contagious stomach illness that causes vomiting, diarrhea, and other gastrointestinal problems. People can contract the norovirus after eating contaminated food or drinking contaminated water, having contact with someone who has it, or placing their hands in their mouth after touching a surface that was contaminated with the virus.
“Lots of nausea, vomiting, explosive diarrhea usually within 12-24 hours,” emergency medicine doctor Frank LoVecchio told AZFamily of the symptoms.
CDC officials say that norovirus outbreaks are common, mostly occurring between the months of November and April. Generally, the virus spreads most quickly when large groups of people congregate in close quarters, such as during cruise trips.
Diarrhea, stomach pain, and vomiting generally start from 12 to 48 hours after exposure to the virus, according to the Mayo Clinic, which added that symptoms generally last one to three days. Most people recover without treatment, although young children, elderly people, and those with compromised immune systems can require medical treatment.