Hawai'i's flu season is in full swing, and public health officials say it's not too late to get immunized.

Doctors participating in the state Department of Health's flu surveillance program are reporting a higher percentage of suspected flu cases among patient visits. During the week of Feb. 11-17, these physicians said that 4.1 percent of patient visits involved people complaining of flulike symptoms, compared with 2.3 percent at the same time last year.

The traditional 33-week influenza season runs from Oct. 1 to May 20. Surveillance data for the 2006-2007 flu season show a steady climb from January on, but the overall outlook is for a relatively mild season, said Ranjani Rajan, Health Department influenza surveillance coordinator.

The 2005-2006 flu season in Hawai'i also was considered mild, with reports rising steadily from the end of 2005 and dropping in February before hitting a peak during the last week of March, according to the Health Department. Another peak occurred in mid-May.

Fifty-nine percent of the patient specimens that tested positive for the influenza virus this season were from schoolchildren and young adults ages 5 to 24. The sick included students at an O'ahu elementary school where a flu outbreak was reported during the week of Feb. 11. Rajan would not reveal the name of the school.

Although the disease is considered a greater threat to the elderly and infirm, everyone should get vaccinated, she said, since younger people who may suffer mild cases of the flu can transmit the virus to more susceptible family members.

"Everybody should get it. Even people who are healthy can transmit the flu, and even if they don't get extremely sick, they can transmit it to higher-risk groups, such as the elderly who live in the household," she said.

Data on the number of actual flu cases in Hawai'i are not available because many people who have flu symptoms never see a physician, and because not all doctors volunteer to participate in the state's flu surveillance program.

Nationally, between 5 percent and 20 percent of the population gets the flu each year, more than 200,000 people are hospitalized from flu complications, and about 36,000 people die, according to the Centers for Disease Control and Prevention.

There is also no data on how many people in Hawai'i have received influenza vaccinations this season, either by injection or nasal mist. Rajan said there is no shortage of vaccine, as in past years.

Flu viruses spread mainly from person to person through coughing or sneezing. Touching something with flu viruses on it and then touching your mouth or nose is another way to get sick.

Symptoms include fever, headache, extreme tiredness, dry cough, sore throat, runny or stuffy nose and muscle aches. Nausea, vomiting and diarrhea are more common in children than adults.

Although public health officials campaign for folks to get their immunizations as early as September, the vaccine is available any time during the flu season and can provide protection from flu viruses.

"It's not too late. It's best to get it early, but if you haven't gotten it yet, there's still a purpose and a point to getting it," Rajan said.

A new immunization is needed for each influenza season, since the vaccine is formulated differently each season depending on which flu "bugs" are circulating.

Flu vaccinations are recommended especially for those age 65 and older, children age 6 months to 2 years, people living in nursing homes or long-term care facilities, pregnant women, and those with diabetes and kidney disease, chronic heart and lung conditions, and compromised immune systems.

Vaccination is the best way to avoid picking up the flu virus and spreading it around, but good hygiene helps. The Health Department recommends washing your hands often with soap for 15 to 20 seconds before rinsing, and rubbing your hands vigorously. Avoid touching your eyes, nose and mouth often, and cough or sneeze into your sleeve or the nook of your elbow.

If possible, stay home from school or work if you are sick, and stay at least three feet away from sick people.