Why Do Hundreds of Grand Canyon Tourists Suddenly Get Sick?

While hiking in Grand Canyon National Park, Kristi Key came across a spot of concern: four hikers resting by the side of the trail, looking a bit battered. After learning that two of the hikers had violently vomited the previous night, Key offered to call a rescue team, but the group declined. But when she saw them sitting in the same spot on her way back, with one of the hikers still spitting up chunks, she knew it was time to call for help.

Finally, a helicopter appeared and brought the sick man to safety. But the experience stuck with Key, who told The Daily Beast that she’s hiked hundreds of miles in the Grand Canyon and has never encountered any hikers whose illness was unrelated to dehydration or heat. After a once-healthy member of the hapless group fell ill later that day, Key began to suspect a virus was to blame.

Key is not alone in her history of nausea as Grand Canyon National Park is currently experiencing an outbreak of a gastrointestinal illness very similar to norovirus, an illness that can cause vomiting, diarrhea, cramps, body aches and a low-grade fever . According to the CDC, norovirus is “highly contagious” and anyone can catch it — the disease can be spread through direct contact with an infected person, contact with a contaminated surface, or ingestion of contaminated food or drink. While symptoms can become very uncomfortable, norovirus rarely causes death or serious illness.

As of June 10, the park was aware of 118 people suffering from gastrointestinal virus, Grand Canyon News reported. The infections spanned 16 separate voyages on the Colorado River and in the backcountry.

A majority of the illnesses were recorded in May, with the most recent case reported on June 2. The park had been on gastrointestinal virus alerts since May 20, according to Jan Balsom, director of communications, partnerships and external affairs in the superintendent’s office at Grand Canyon National Park.

“We haven’t seen an eruption like this in about 10 years,” Balsom said. In fact, Balsom herself had an encounter with what she called the “unusual” prevalence of gastrointestinal problems when a woman on a recent river cruise she took part in contracted a stomach virus less than 12 hours after the trip. However, the woman does not know if she was infected with norovirus or another disease, a predicament that illustrates many of the difficulties in investigating the outbreak.

There is a limited time when one can collect stool samples to confirm norovirus infection, Balsom said. River trips usually outlast this critical window, meaning it’s often impossible to accurately diagnose a person’s illness.

The park asks visitors to ensure their water isn’t just filtered, as norovirus isn’t killed by point-of-use filters. It must be either chemically disinfected or boiled. It is also asked that visitors do not drink from waterfalls, pools or streams.

A public health team made up of various state and federal agencies is investigating the outbreak. Balsom explained that the Colorado River and the backcountry are unconnected areas, adding to the mystery of the falls.

“[Officials] have conducted interviews with participants of trips who have fallen ill,” Balsom said. “They tested poop scans to determine if it was noro or not.”

In a statement to The Daily Beast, an official with the National Park Service Office of Public Health described the outbreak as “elevated GI disease” and said an investigation would “consider all potential sources.” It is currently unknown what is causing the disease.”

Individuals have taken to social media to share their stories of trips cut short by vomit and posted lengthy sagas of hikes that went horribly wrong.

One man wrote that he was overcome by vomiting in the middle of the night, with his bouts of nausea lasting from 1am to 5am

“Let me tell you,” he wrote, “to be sick and weak and to hike 1,200 feet in elevation 1.5 miles is not exercise.”

In another, posted to the Grand Canyon Hikers Facebook group in May, a woman informed others about the norovirus outbreak and described how she became ill soon after leaving the canyon.

“I wouldn’t have been able to hike or take care of myself if I started throwing up in the canyon,” she wrote. “GC health authorities are monitoring the situation. Apparently it’s a big one.”

A big one – and smelly one – indeed.