As the Indian summer sets, so does the onset of flu season that brings with it the fever, chills, cough, muscular achiness, extreme fatigue and nasal congestion that wreaks havoc on our bodies.

The height of the flu season occurs in late December and early January so if you've been considering vaccination, the next two months is an optimal time since the vaccine begins to protect you after one to two weeks.

There is no such thing as "the flu bug" since influenza is not caused by bacteria or a parasite. In fact, although it affects millions of people worldwide each year, it is one of the most misunderstood common ailments. "The flu" is commonly used as a catchall term for winter colds and many other conditions that cause nausea, diarrhea and vomiting, but it is actually a potentially life-threatening, contagious lung disease caused by a virus. The virus attacks and temporarily damages the lining of the respiratory tract, causing the tissues to become swollen and inflamed. The virus may be passed to others through coughing or breathing, especially in the first four days of the illness. Most people recover and heal unscathed within two weeks. However, influenza can weaken your body, predisposing you to its most common complication -- pneumonia. Flu and pneumonia combined are responsible for more than 20,000 deaths nationwide each year -- the fifth leading cause of death among all Americans over 65.

There are two basic types of viruses which can cause the flu: Influenza A and Influenza B and each of these may be divided into subtypes, based upon differences in the viral proteins. Influenza viruses continually change over time, consequently each year the influenza vaccine is updated to cover the most current viral changes.

Your mother was right: rest and drinking lots of fluids helps speed your recovery, but fortunately there are now prescription anti-viral medications that can arrest viral replication. If taken within 48 hours of onset of symptoms, you can feel better on the second day of treatment and since it stops the flu virus from reproducing in your body, you are no longer contagious.

Who needs the influenza vaccine? Anyone who wants a 70-90 percent reduction in his or her chances of getting the flu. It is especially recommended for persons aged 65 years or older and for residents of nursing homes and other chronic patient care facilities. Health care workers are also at increased risk. Adults and children with chronic lung and heart system disorders, as well as those with immunosuppression and diabetes mellitus are at increased risk. Further, pregnant women who will be in their third trimester of pregnancy between December and April should consult their physician about receiving the influenza vaccine during September to mid-November.

Whichever type of virus you contract, there is no substitute for the tender loving care of a close family member. And don't forget mom's advice: Get plenty of rest and drink extra fluids to speed your recuperation.

Worldwide Web Resources

American Lung Association

www.alaw.org/ifp.html

The American Lung Association of Washington has an excellent Web page that provides 1998 data on influenza, pneumonia, and vaccine recommendations from the Centers for Disease Control.

The Idaho Falls Recovery Center

ifrc.ida.net/flufacts.htm

This Web site covers "Facts About Flu (Influenza)" and "What You Can Do to Fight the Flu."

Prevention for Seniors

www.hapcorp.org/docs/HEALTHY/Influenz.htm

Facts about influenza that are of particular concern for senior citizens are highlighted at this Web site.

Dr. Scott Gibbs is a neurosurgeon and editor-in-chief of Mosby's Medical Surfari. You may e-mail questions to him at drgibbs@semissourian.com or write in care of the Southeast Missourian, P.O. Box 699, Cape Girardeau, Mo., 63701.