Flu Vaccine, a Master of Disguise, Travels Far

A worldwide traveler and master of disguise, the virus that causes flu is associated with 10,000 deaths a year, according to the Centers for Disease Control in Atlanta.

Millions died in 1918 when a particularly virulent strain appeared.

“No other respiratory illness carries such a high mortality,” said Dr. Stephen Baum, professor of medicine and cell biology at Albert Einstein College of Medicine.

The virus--and flu--circles the globe, leaving behind a number of people who should be immune by the time it returns the next year.

But because of its disguises, it often fools the body into thinking it’s a new virus.

“It has tendency to mutate very slightly from season to season,” said Bill Fagel of the New York state Department of Health. “Since last year it may have mutated just enough so if you had a case last year and get it this year, you’ll have a milder case.”

The more drastic the mutation, the more people that get sick and the sicker they tend to be.

There are three types of flu virus, with strains of each type that are named for the place where the strain was first identified.

A worldwide monitoring system tracks flu’s movements and documents changes in the viruses and new strains. From that information, the CDC predicts what strain will hit the United States and develops a vaccine to protect people who might be most susceptible to flu’s deadly effects, said Dr. John R. La Montagne of the National Institute of Allergy and Infectious Diseases in Bethesda, Md.

Older and unhealthy people, especially those in nursing homes, are advised each fall to take the vaccine. However, if someone has missed getting a vaccination this year, it’s not too late--but they had better hurry, said CDC officials. Flu season usually peaks in February.

Some scientists say the reason a “flu season” exists at all is that the virus survives better in cold, dry air. Others think it’s not the weather, but how people react to it.

“It’s probably that people are gathered together in closed spaces and are able to transmit the disease readily,” Baum said.

Cold might not have much to do with it, he added, since in the tropics, flu peaks during the summer when heavy rains drive people indoors.

Many people blame the flu bug for all their winter ills, but the influenza virus, a microscopic “bullet” filled with genetic material, attacks the respiratory system and leaves the stomach and head for other viruses to ravage.

If the body recognizes the virus as one that has invaded before, then it can squash the infection before symptoms appear with antibodies developed by the immune system during the last invasion of a particular virus.