Four people who live in the same Pearl City neighborhood are the first known Hawaii cases of locally contracted dengue fever since a 2001 outbreak in which 153 people were infected with the mosquito-borne viral illness, health officials announced yesterday.

A Pearl City woman who traveled to Wisconsin last month was hospitalized for high fever, among other symptoms, and was diagnosed with dengue fever after a blood test for the disease came back positive.

Also showing symptoms of the disease are two adults who are members of her family and their neighbor. None has traveled elsewhere.

Two cases are confirmed, and the other two are awaiting test results.

"It’s certainly possible, given that we’ve found this cluster of four — two of whom were not diagnosed by their clinicians — it’s entirely possible there were others," said state Epidemiologist Sarah Park. "You only need one person infected who has the virus in their blood and they get bit by a mosquito, and you have a mosquito that’s infected."

Park likened it to drug users spreading disease by sharing dirty needles.

All prior known Hawaii cases of dengue since the outbreak a decade ago were imported, said Gary Gill, deputy director for environmental health.

No deaths have occurred, even during the 2001 outbreak.

The data show that from 2002 to 2009, cases ranged from three to 14 a year. One year had no cases.

"This is a good wake-up call for all of us, especially to us clinicians," said Park. "Mainland docs think we have dengue all the time. We generally say it’s not endemic here."

Park said that after the woman went to the Wisconsin hospital with severe symptoms, the doctor surmised, "’Hmm, comes from Hawaii,’ and did the dengue test."

The Health Department sent out a medical alert to Oahu physicians this week, advising them to consider the potential for dengue infection in those with compatible symptoms, to request laboratory testing and to report all suspected cases to the Health Department.

The symptoms usually start five to six days after a patient is bitten by an infected mosquito, but the onset can range from two to 15 days. Symptoms include a sudden fever, severe headaches, pain behind the eye, joint and muscle pain and rash — typically on hands, arms, legs and feet three to four days after the fever starts.

Park said the symptoms ranged in severity, with the youngest of the four Pearl City adults having the mildest symptoms.

Park expressed concern that people have been complaining of flulike symptoms might have had the disease. Usually a severe fever that "feels like your bone is breaking" accompanies the ailment, she said.

Younger children tend to have milder symptoms and might show none.

There is no vaccine for dengue fever. Acetaminophen (Tylenol) can be used to reduce fever, but since bleeding can occur, aspirin and ibuprofen or naproxen (which can worsen bleeding problems) should not be used.

Dengue fever also can result in seizures. But just as the fever is resolving, it can progress to dengue hemorrhagic fever, Park said. This next stage is marked by abnormal bleeding and shock.

CONTROLLING MOSQUITOES » Empty and clean flower vases at least once a week. » Spray the surface of breeding areas (such as unused swimming pools or other areas of standing water) with 4 to 6 ounces of liquid dish detergent in a gallon of water. Repeat every two to three days. Not for catchment tanks or drinking water. » Make sure water catchment tanks are mosquito-proof. » Eliminate adult mosquitoes indoors with aerosol insecticides labeled for flying insects. » Remove, repair or empty anything that collects rainwater, such as cans, bottles, buckets, used tires, flowerpots, bromeliad plants, pineapple lilies, clogged roof gutters, hollow bamboo or tree stumps, uncapped hollow tile walls, uncapped fence pipes, abandoned cars and boats. » Check all screen doors and windows and repair as necessary. » Empty and clean animal-watering containers at least once a week. Source: State Department of Health

The disease is transmitted to humans by mosquitoes, which become infected after biting humans with the disease, and cannot be transmitted from human to human.

To prevent the disease from spreading, the Health Department advises people with dengue to remain indoors to avoid being bitten by mosquitoes and possibly pass the dengue to another person. The department also urges the public to remove standing water from places in their yards such as gutters, old tires and bromeliads where water collects, which could serve as mosquito breeding grounds.

"We expect to see tight concentrations of the disease and in small areas," said the Health Department’s Gill.

The Health Department has sent out vector control, sanitation and epidemiology personnel to the 70 people in the Pearl City neighborhood. So far, 10 people have had their blood drawn for testing.

Health Department officials said they don’t know whether there might have been prior cases of dengue fever transmitted by local exposure.

An infected mosquito can spread it not only to other humans, but among their pool and to their offspring, Park said.

Gill emphasized the species of mosquito in Hawaii that transmits the disease, Aedes albopictus, does so inefficiently.

In 2001 the disease was concentrated in East Maui, but confirmed cases were found on Oahu, Kauai and the Big Island.

Health officials believed the virus was brought to Maui by visitors who had traveled to French Polynesia and the Samoas.

Prior to that, Hawaii’s last major outbreak, with 1,200 cases, came at the end of World War II, resulting in several deaths.