Dozens fall ill on Hawaii hiking trail in ‘concerning’ outbreak of norovirus

A popular hiking trail on the island of Kauai in Hawaii was closed this week after more than three dozen people fell ill in what officials said was a “rare occurrence” of the highly contagious norovirus.

The Kalalau Trail, a 22-mile round-trip stretch within the Napali Coast State Wilderness Park, was recommended to remain closed until at least Sept. 19 while Department of Health officials assessed the ongoing risk of transmission and as stations along the trail were cleaned and disinfected.

The Health Department received reports of illness from at least 37 hikers and campers over the past several weeks, though the actual number is expected to be higher, officials said.

“This is a very concerning and rare occurrence, magnified by the extreme remote nature of the Kalalau Valley,” Curt Cottrell, an administrator for state parks, said in a statement.

The trail was closed Wednesday after health officials received numerous reports of gastrointestinal illnesses from hikers, and Thursday the Health Department said that test results from four patients confirmed that they had contracted norovirus.

The state’s Department of Land and Natural Resources said in a statement that dozens of backpackers along the trail had reported gastrointestinal illness, and that one person had been evacuated but no one had been hospitalized.

The source of the outbreak remained under investigation.

“All it takes is one person to spread the virus, which can be on surfaces, in the soil and in water,” said Dan Dennison, a spokesperson for the Department of Land and Natural Resources.

Norovirus is highly contagious and typically causes vomiting, often accompanied by fever, abdominal cramps and diarrhea as the stomach or intestines become inflamed.

It spreads easily, and is common in tightly packed spaces, such as cruises or nursing homes, but it can also be transmitted across contaminated surfaces.

“It’s incredibly infectious,” Donald Schaffner, chair of the Department of Food Science at Rutgers University, said Saturday. “People that are sick with norovirus are shedding literally billions of virus particles. And it doesn’t take that many virus particles before you have a reasonable chance of getting sick.”

Most people completely recover from the virus after several days, but severe infections can occur in young children, older adults and people with weakened immune systems.

Even in an outdoor environment, Schaffner said, people might not be protected against transmission, either through close contact or the contamination of shared facilities.

The Kalalau Trail allows up to 80 people with permits to camp overnight, and composting toilets are available. One way that norovirus can spread is through contact with fecal matter.

The open air might help dilute the virus “but mostly it’s just being around people that are ill and shedding the virus” that aids in spreading it, Schaffner said.

The spread of norovirus in a ventilated environment such as a trail “is possible due to virus transmissibility and challenges to hand hygiene and sanitation,” the Department of Land and Natural Resources said.

Norovirus was detected in multiple tests of people who had been on the trail but who did not directly interact with one another, the department said.

“Hiking is one of the activities that is a risk” for the virus, said Dr. Stuart C. Ray, a professor of medicine and infectious diseases at the Johns Hopkins School of Medicine in Baltimore. “The problem is that people don’t have good access to clean water, and they can’t wash their hands.”

Alcohol gels and wipes do not kill norovirus, he said, adding, “We have rules in health care that if someone has norovirus, it’s soap and water only.”

In March, the National Park Service issued an alert for hikers on the Appalachian Trail in Georgia and Tennessee, warning them about an increased risk of gastrointestinal illnesses related to norovirus.

In 2022, an outbreak of an illness, which the U.S. Centers for Disease Control and Prevention said was likely norovirus, infected more than 200 rafters and backpackers in the backcountry of Grand Canyon National Park.

People who contract norovirus should consider themselves infectious for at least a few days, even after they recover. A symptomatic person who did not report their illness or did not realize they were sick is one possible cause for the outbreak on the Kalalau Trail, Ray said.

Schaffner and Ray said it’s extremely difficult to pinpoint the source of an outbreak.

“We often never know who patient zero was,” Ray said.

This article originally appeared in The New York Times.