State officials are now closing the entire Kalalau Trail at Napali Coast State Wilderness Park on Kauai due to a confirmed outbreak of the highly contagious norovirus.

The closure now extends along the entire Kalalau Trail section, from Kee to Honopu, in the park.

The Hawaii Department of Land and Natural Resources is also extending the closure to at least Sept. 19, longer than the initial 7-day period announced.

DLNR on Wednesday closed most of the trail and campsite, upon the state Health Department’s recommendations, due to a suspected norovirus outbreak, which laboratory results have since confirmed.

At least 37 people, to date, have reported illnesses to the state Health Department after hiking and camping at Kalalau, with the actual number believed to be higher. Officials said norovirus was detected in multiple samples of people with no direct interaction with each other.

State conservation officers have flown into Kalalau to inform campers that they need to leave, and the Kalalau Trailhead at Kee will be manned by law enforcement 24/7 to prevent entrance onto the trail.

All comfort stations along the trail are being cleaned and disinfected.

The Hawaii Department of Health also sent a team to Kalalau to collect water, soil, and environmental swabs to assess the ongoing risk of transmission from contaminated surfaces or water.

DLNR said commercial and recreational boaters should not drop people off to swim, paddle, or kayak at Kalalau beach. Anyone caught trespassing can be cited or arrested during the closure, DLNR warned.

“It is imperative to keep humans out based on the DOH protocols,” said DLNR in a news release.

Norovirus is a very contagious virus that causes vomiting and diarrhea, according to U.S. Centers for Disease Control and Prevention.

People can become infected with norovirus through direct contact with someone with the virus, by eating or drinking contaminated food or water or by touching contaminated surfaces and then their mouths.

Symptoms, which usually begin about 24 to 48 hours after exposure, include nausea, vomiting, diarrhea and stomach cramps — and sometimes fever, headache and body aches.

Most people with norovirus illness get better within one to three days, according to CDC, but can still spread the virus a few days after.

DLNR said individuals who recently hiked the trail should monitor themselves for symptoms. If symptoms are severe, or do not resolve within one to two days, people should seek medical care promptly.

To report an illness, contact the DOH Disease Investigation Branch on Oahu at 808-586-4586.