Rumblings of the upcoming flu season have begun and health authorities are responding with a recommendation for more people than ever to protect themselves with immunization shots.

Like frost on the pumpkin, flu season predictably appears in late fall and early winter, striking millions in the United States and killing from 10,000 to 20,000 people, most of them over age 65.Yet, 80 percent of those most vulnerable to the ravages of flu don't get immunized, nor does most of the general population.

"Most people think of the flu as no more than a bad cold, and they're wrong," said Dr Frederick Ruben, an influenza specialits with the American Lung Association.

"Get a flu shot each year so you won't get sick yourself or bring home the virus to someone you care about," he urged.

In line with new efforts by the federal Centers for Disease Control to decrease deadly flu complications, the ALA broadened its immunization call for the first time this year to include people sharing households with the elderly or others at high risk, Ruben said.

"We must draw a ring of immunity around our senior citizens and others who are most vulnerable," Ruben said, adding, "The CDC has underlined this as being a new approach to controlling mortality and morbidity from the flu."

Less predictable than the start of the flu season is the shape of each year's epidemic, which varies due to the regular mutations of the influenza virus.

"I don't think it is even as easy as predicting the weather, to be honest," said epidemiologist Suzanne Gaventa, the CDC's national influenza surveillance coordinator.

One case has been confirmed so far this year--a 32-year-old Wisconsin woman who developed flu while pregnant and was hospitilized with viral pneumonia, Gaventa said.

The woman subsequently delivered a health infant, but died of the pneumonia; a strain of swine flu virus was isolated and confirmed as the cause.

But, Gaventa said, such an isolated case cannot predict the type of flu virus that will predominate this year.

"The virus is continuously mutating to evade the humas immune system," she said. Based on internationally gathered date, scientists developed a vaccine this year targeting two Type A strains (H1N1 Taiwan Flu and H3N3 Sichuan flu) and one Type B strain (Victoria flu).

The vaccine will be distributed free to millions of elderly Americans as part of a demonstration project testing the cost-effectiveness of flu prevention. The $25 million effort for Medicare recipients will be run at selected sites around the country, said Ron Teske, CDC coordinator for the project.

In spite of late distribution due to difficulties growing the virus, plenty of vaccines should be available for the project and the more than 21 million Americans expected to get shots this year, Teske said.

Influenza is communicated through the air in respiratory droplets and the season is thought related to seasonal clustering of people inside.

Fever, chills, weakness, loss of appetite, general achiness and exhaustion can overwhelm the body for days, but sometimes healthier people suffer the most severe symptons, while weaker individuals can be the more seriously ill.

"Many, many times, I've seen elderly persons with just a fever and no more than a cough, and then in a couple of days, they're dead from the flu," said Ruben, a professor of medicine at the University of Pittsburgh School of Medicine.

Flu season starts this month in the United States and continues until April, peaking from January through March. Vaccinations are recommended before mid-November to allow time for sufficient antibodies to develop before the peak period.

Only people who are allergic to eggs should not get vaccinated because the vaccination material is grown in chicken eggs. Such people could benefit from takingamantadine, an anti-viral drug that can block infection and alleviate symptons should infection occur. However, it is not effective against influenza B.

Flu shots are recommended most strongly for the elderly and people with health problems, such as any chronic lung or heart disease, diabetes, kidney ailments, anemia, HIV infection or AIDS, any other immune-suppresive condition due to disease or medical treatment, and children over age of six months and teenagers up to 18 years receiving long-term aspirin therapy, because of the risk of Reye's syndrome following flu infection.