The gangplank was hardly down before Internet chat rooms were blowing the event out of proportion. Some claimed that all the passengers — about 2,000 — were confined to their cabins and going hungry because room service was slow.

The actual number of passengers who stayed aboard was 17, according to Dr. Lorrin Pang, Maui District health officer with the state Department of Health. They did so voluntarily, after receiving medical advice.

Cruise ships are an ideal environment for noroviruses, formerly called Norwalk virus, although Pang said he only suspected norovirus. The Maui District Health Office did not have a firm diagnosis Friday but should sometime next week when laboratory results are returned from Honolulu.

The test cannot be done on Maui.

Pang said that if this week's event is confirmed as a norovirus, it would be the fourth on a cruise ship here in the past two years.

The disease is acutely unpleasant, with violent vomiting and diarrhea, but usually brief, about 48 hours. It can, however, be dangerous to young or elderly people, who can become dehydrated, sometimes fatally.

Pang encountered the virus while working in Louisiana in the aftermath of Hurricane Katrina.

His first action after learning that norovirus or something like it might be around was to contact organizations that take elderly people on trips (such as Hale Makua) and ask them not to go where cruise passengers go.

"For the first time, we are getting 110 percent complete cooperation," said Pang. The reason that noroviruses like cruise ships is that they can exist much longer, up to three weeks, in air-conditioned places, compared with Hawaii's temperatures.

Also, because the vomiting is so violent, Pang says, the virus is sprayed in an aerosol "all over," up to ceilings. It is difficult to clean up, because everything has to be scrubbed down, not just visible traces.

A special cleaning team was being scrambled from Oahu by NCL to disinfect the ship. Pang said he was told the disinfectant team will also treat places where sick passengers or crew might have been on shore.

NCL officials in Honolulu could not be reached to confirm this.

Pang was told that the outbreak of illness aboard ship started Monday, but since the infection runs its course quickly, there were only dozens of passengers and crew ill at any one time.

The Pride of Hawaii would ordinarily have been docked in Kahului Thursday, but it went to Kona because a special cleaning team from Oahu was flown in to clean up a small spill of heavy oil. Harbormaster Steve Pfister said the team was still working around Pier 1 Friday, but he judged that the cruise ship would not be in the way.

Because noroviruses can also be spread by food, the Food and Drug Administration is the federal agency responsible for identifying, monitoring and managing outbreaks, not the Centers for Disease Control.

However, the CDC has information about noroviruses on its Web site. As for prevention, the advice, Pang says, is, "Wash hands, wash hands, wash hands."

When he visited Pier 1 Friday morning, "they were washing their hands."

According to the CDC, the symptoms of norovirus illness usually include nausea, vomiting, diarrhea and some stomach cramping. Sometimes people additionally have a low-grade fever, chills, headache, muscle aches and a general sense of tiredness. The illness often begins suddenly, and the infected person may feel very sick.

The problem with an outbreak on a cruise ship, Pang says, is that people "feel fine" until just before they get sick.

They leave the ship to tour the island and then find themselves feeling wretched in a strange place.

Although familiarly called "stomach flu," a norovirus infection is not a flu, which is a respiratory illness, but a kind of gastroenteritis.

There is no vaccine against norovirus, and antibiotics are useless since they attack bacteria and not viruses.

NOROVIRUS ATTACKS

While the cause of illness aboard the Pride of Hawaii has not been confirmed, health officials caution Maui residents to be aware an outbreak of norovirus may have occurred.