State officials have closed Kalalau Valley at Napali Coast State Wilderness Park on Kauai due to an outbreak of suspected norovirus, effective today.

The state Department of Land and Natural Resources closed the hiking trail and campground upon the recommendation of the Hawaii Department of Health due to the high risk of illness in the isolated setting.

DOH has recommended that the trail be closed for seven days.

Since Aug. 14, DOH has received reports of acute gastrointestinal illness, with symptoms such as nausea, vomiting and diarrhea from 24 people who have hiked the Kalalau Trail. One required evacuation. None have been hospitalized.

While the type of illness among hikers has yet to be confirmed by laboratory tests, health officials believe it is norovirus based on reported symptoms.

People can become infected with noroviruses — a group of viruses that cause gastroenteritis — by eating or drinking contaminated food or water or by touching contaminated surfaces and then their mouths.

Norovirus can also be found in shellfish, particularly oysters and clams, and in produce washed with contaminated water.

Symptoms, which usually begin about 24 to 48 hours after exposure, include nausea, vomiting, diarrhea and stomach cramps — and some may also experience mild fever, chills, and muscle aches.

The illness is usually short, with symptoms lasting about one or two days.

DLNR said individuals who recently hiked the trail should monitor themselves for symptoms.

The reported illnesses have been self-resolving, officials said, but if symptoms do not improve within one to two days or are severe, people should seek medical care promptly.

DLNR’s Division of State Parks reported that one sick camper had hiked out on Monday, while other seriously ill campers were said to have departed by boat.

Officers will fly in to the park to inform hikers in person of the closure between Hanakapiai and Kalalau. Two officers will also hike into Kalalau to check on the welfare of campers at the site, and call for further medical assistance if needed.

“This is a very concerning and rare occurrence, magnified by the extreme remote nature of the Kalalau Valley,” said DSP Administrator Curt Cottrell in a news release. “We appreciate the DOH guidance in helping manage and mitigate this isolated outbreak in the hope no one else is exposed or gets sick.”

The reopening of Kalalau is subject to change, based on additional guidance from DOH, officials said.

Permit holders for the closed dates can request a refund or rebook to a later date by emailing DLNR.DSP.Permits@hawaii.gov.