National Park Service Investigates Mystery Illness Among Grand Canyon Rafters

In an emailed statement to NTD, the federal agency said that it is working with health officials on further examining reports of sicknesses among those who rafted the Colorado River.
Published: 7/8/2026, 10:06:06 PM EDT
National Park Service Investigates Mystery Illness Among Grand Canyon Rafters
The Colorado River at the Grand Canyon National Park, in Ariz. (Brian Witte/File via AP)

The National Park Service (NPS) has launched an investigation into the cause of a mysterious illness affecting rafters in the Grand Canyon.

In an emailed statement to NTD, the federal agency said that it is working with health officials on further examining reports of sicknesses among those who rafted the Colorado River.

“The National Park Service has received reports of individuals experiencing symptoms including fever, chills, fatigue, headache, difficulty breathing, muscle or body aches or soreness, joint or bone pain, or localized swelling following river trips on the Colorado River through Grand Canyon National Park,” the statement read.

“The National Park Service Office of Health and Safety is coordinating with public health partners to review these reports," NPS added.

The agency did not disclose the number of reports it has received or specify dates of the rafters' trips.

Utah resident Matthew Wappett said he reported his symptoms to the NPS. Wappett shared his own experience on social media of a mysterious, lingering illness following a rafting trip on the Colorado River in mid-May. Three days after returning home, he said that he went to the emergency room with a massive knee infection and “bone-crushing aches” in his joints. He was later diagnosed with cellulitis.

According to Wappett, antibiotics helped his knee infection, but he eventually felt a sickness that progressed into pneumonia and flu-like symptoms that continued on for more than a month.

“Not sure what this is, but I wouldn't wish this misery on my worst enemy....it's really taken a toll on me physically and mentally,” he wrote on Facebook.

Wappett also noted that he got some mosquito bites during the trip.

After posting his ongoing ordeal in a Grand Canyon rafters’ Facebook group, Wappett said that he discovered that several other rafters from various boating groups were battling the same lingering symptoms.

Another rafter, Steven King, shared a similar experience in the Facebook group, sharing that four of his fellow traveling companions out of a group of 16 had suffered symptoms, including fever, chills, weakness, and fluid in the lungs. ​

“Doctors are all stumped so far but are conducting lots of blood work/ tests,” King wrote.

According to King, doctors suggested that one of his traveling companions had pneumonia, while another tested positive for cellulitis.

King noted that they noticed a few mosquitoes on several nights of their trip.

Both King and Wappett said that they both traveled from Lees Ferry to Diamond Creek, a popular 225-mile Colorado River rafting and kayaking route through the Grand Canyon.