Everything you need to know about the PCT norovirus outbreak

TO A severe outbreak of acute gastroenteritis (a stomach flu commonly caused by the highly contagious norovirus) has hit the Pacific Crest Trail (PCT) in Southern California, forcing public health agencies and trail organizations to mount an emergency containment effort.

The Pacific Crest Trail Association (PCTA) has issued an official alert confirming reports of widespread gastrointestinal illness affecting hikers between trail miles 298 and 374, an area encompassing Swarthout Canyon and the town of Wrightwood.

At this time, there is no confirmed source of the reported illness. However, laboratory testing at urgent care clinics in Hesperia, Victorville and Lancaster has confirmed that at least 7 to 12 hikers contracted norovirus, and more than two dozen more reported identical, debilitating symptoms.

Norovirus on long-distance trails

The current outbreak began about a month ago near Wrightwood, located 77 miles northeast of Los Angeles. While nationwide norovirus typically peaks during the winter months, rapid transmission among hikers in bubbles on long-distance trails leads to an anomalous surge in the late spring and summer months.

Norovirus is an incredibly resistant virus and very difficult to kill. It can survive on hard surfaces for weeks and can even withstand temperatures up to 145°F, meaning boiling water won’t automatically destroy it. To make matters worse, it is wildly contagious. It takes only 18 to 20 microscopic virus particles to make a healthy person seriously ill; However, an infected person sheds billions of these particles every time they vomit or use the bathroom.

When a backpacker contracts norovirus, the symptoms combined with their physical needs can quickly become dangerous. The sudden onset of projectile vomiting and severe diarrhea causes rapid dehydration. In remote wild environments where drinking water is scarce, this can quickly lead to decreased cognitive function and cardiovascular stability.

On May 14, a 73-year-old hiker near Mount Baden-Powell suffered severe weakness and could not stand. Emergency search and rescue personnel had to execute a complex helicopter evacuation to transport the hiker to a medical center in Lancaster to treat norovirus-induced dehydration.

Mount Baden-Powell. Photo via Lauren Singer

What started the PCT norovirus outbreak of 2026?

While there is no confirmed location of the outbreak, one source of transmission is suspected: an unofficial, volunteer-run water tower in Swarthout Valley at mile marker 347.3.

The PCT in Southern California is notoriously dry, and hikers must juggle long hauls of water. Well-meaning trail angels often install water reservoirs in open containers at road crossings, providing water and a place for hikers to gather and camp together.

On May 10 and 11, eyewitness reports detail that two infected hikers camped within 5 to 20 feet of the Swarthout Valley water reservoir. Both were actively vomiting and using shallow catheters and may have contaminated the handles of shared water jugs. Because norovirus has an incubation period of 12 to 48 hours, these two hikers likely contracted the virus further south and hiked for miles before realizing they were sick and spreading the pathogen along the trail.

Dozens of hikers who arrived later and handled the containers contracted the disease.

Standard Backpacker Hygiene Doesn’t Kill Norovirus

Most hikers rely on alcohol-based hand sanitizers as their primary method of hygiene. However, due to the biological structure of norovirus, disinfectants containing 60% to 95% alcohol cannot neutralize it. Soap and water also do not kill the virus, but act as surfactants to mechanically loosen and rinse particles from the skin in a way that hand sanitizers cannot replicate.

And, in the unfortunate case of an infected water source, most filters may not be up to the challenge either. The vast majority of backpackers use hollow fiber membrane microfilters with a pore size of 0.1 to 0.2 µm, such as the Sawyer Squeeze, which has a pore size of 0.1 µm. While they are very effective against bacteria and protozoa such as giardia, these pores are too large to trap norovirus, which measures a tiny 0.03 µm. The virus passes directly, intact, through standard filters.

Coordinated public health response

To contain the spread, PCTA is coordinating directly with the California Department of Public Health, San Bernardino County Public Health Department, and the U.S. Forest Service to distribute necessary information to the trail community.

To start, volunteers removed all open and shared water containers from the Swarthout Valley Cache, replacing them with sealed, single-use bottles, while local lodges and lodges in the Wrightwood area temporarily closed to PCT hikers to stop transmission in high-density indoor environments.

The San Bernardino County Department of Public Health has launched an official program health survey for anyone who has been affected or has relevant information about their time on the trail in this area. Survey responses go directly to public health officials, not the PCTA or the US Forest Service. All specific health questions should be directed to the San Bernardino County Department of Public Health.

Hand washing station in a water tank. Photo via Sage Wagner

Norovirus prevention recommendations for hikers

Public health officials have stated that backpackers must change their habits to break the chain of transmission. Instead of relying on hand sanitizer, wash your hands vigorously with biodegradable soap and clean water at least 200 feet away from natural water sources after using the bathroom and before eating. And, because standard filters fail against viruses, hikers in the outbreak zone should use secondary chemical disinfection (chlorine or iodine) or boil water for at least 1 minute (3 minutes if above 6,500 feet).

Finally, any hiker who experiences acute vomiting or diarrhea should immediately isolate themselves from others, stop handling shared food, and leave the trail to quarantine. Infected people remain highly contagious and must remain isolated for at least 48 hours. after All symptoms have completely resolved.

Featured image via Zach Davis

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