Grand Canyon campers are contracting norovirus, causing diarrhea and vomiting on rafting excursions

• Backcountry campers and river rafters at the Grand Canyon have reported outbreaks of gastrointestinal illness.
• At least 150 visitors to the national park showed symptoms of norovirus, including vomiting and diarrhea.

More than 150 visitors to the Grand Canyon have gotten sick with gastrointestinal illness in what officials are calling an "unusual" outbreak of norovirus.

One hiker, Kristi Key, told the Daily Beast that she called for an evacuation after coming across four hikers who seemed to be ill. Two of them had spent the previous night vomiting, and one was still throwing up when she hiked back to them later that day. The men were eventually flown out of the park by chopper, thanks to Key's call for help.

Norovirus is a highly contagious virus that causes a sudden onset of vomiting and diarrhea, which can last up to three days. The illness spreads through contaminated food, drinks, and surfaces; or through direct contact with a sick person.

The virus was confirmed to have sickened people on at least eight river rafting trips in the national park between April and May 2022. Some campers who did not go rafting also reported getting sick with nausea, stomach cramping, vomiting, or diarrhea.

Reports of illness have declined since early June, according to a press release from park officials.

It's rare to see an outbreak of norovirus linked to a national park, officials told the Washington Post. The virus is commonly associated with cruise ships where people live in close quarters, although outbreaks on ships are not as frequent as people may think, according to the Centers for Disease Control and Prevention.

Commercial rafting trips through the Grand Canyon can last anywhere from three to 18 days, according to the National Park Service. Private excursions may take even longer. During a week or two on the river, there are plenty of opportunities for direct contact with the virus.

The virus spreads through close contact with poop particles

Sharing food or drinks with someone infected with norovirus — especially if they haven't washed their hands since going to the bathroom — is a common mode of transmission. Any situation where tiny particles of poop or vomit make it from an infected person into your mouth poses a risk of infection.

Park officials have implemented "comprehensive control measures" to limit the spread of norovirus at the Grand Canyon, such as warning people to use separate plates, bowls, and utensils. Officials also urged visitors to use designated toilet areas or sealable containers to carry human waste out of the canyon.

It's also possible for water sources to be contaminated with norovirus. Grand Canyon visitors are instructed to only drink water from park-provided fountains and spigots, as natural water sources are no longer considered safe to drink.

To prevent the spread of norovirus via drinking water, any water collected from rivers, waterfalls, or pools must be chemically disinfected or boiled at a roiling boil for at least a minute.

Norovirus typically passes after one to three days of illness, which can begin 12 to 48 hours after exposure. Individuals who have recently been sick or exposed to people with gastrointestinal illness should not join group trips, according to the National Park Service.

If a traveler gets sick on a trip, they should be separated from the group to prevent the spread of illness. Severe cases of norovirus may lead to dehydration, which could require evacuation by helicopter in extreme circumstances, officials told the Post.