When cold sufferers are most likely to pass along the misery

Medical Matters

November 11, 2005|By JUDY FOREMAN

How long are you contagious when you have a cold?

It depends on which virus is causing the cold, and there are lots - including rhinoviruses, adenoviruses and coronaviruses, to name a few, said Dr. Lindsey Baden, an infectious disease specialist at Brigham and Women's Hospital in Boston.

Typically, you are most likely to spread the virus to other people from a point just before symptoms appear through the first few days of an illness, when symptoms such as coughing, sneezing and production of nasal mucus are highest.

Dr. Jack Gwaltney, professor emeritus of internal medicine at the University of Virginia School of Medicine, has done research that shows the virus starts reproducing within a half-hour of entering the nose. It takes only eight to 12 hours for new virus to appear in nasal mucus.

This rapid production of the virus lasts about three days - the days when you are most contagious - and then falls off as the immune system gears up and finally begins to kill the virus. One study showed that when one spouse is experimentally infected with a virus, the other spouse typically gets infected within the first three days.

Since it's mucus from the nose that is the main carrier of viruses, you should dispose of tissues yourself.

It also pays to wash your hands, whether you're the one who's sick or the one trying not to become the next victim.

Once you start feeling better, the virus may still be present in your nose for as long as two weeks. But you are much less contagious.

As for antibiotics, they don't do anything for viruses. But if your "cold" is actually a bacterial infection, antibiotics will help with that and will make you less contagious while you are taking them.

If exercise generates free radicals and free radicals are bad, why is exercise good?

Free radicals, forms of oxygen that are missing an electron, are actually not all bad.

Although free radicals can destroy cell membranes and DNA, scientists have discovered that they are also "good," said Dr. John McDonald, a neurologist at the Kennedy Krieger Institute and Johns Hopkins. For instance, they help with cell signaling, the process of chemical communication that tells a cell, among other things, when to activate certain genes.

Exercise does generate free radicals, but it also boosts production of molecules that sop up free radicals, said William J. Evans, an exercise physiologist at the University of Arkansas for Medical Sciences in an e-mail.

In other words, regular exercise actually "trains the antioxidant system," boosting production of natural antioxidants such as SOD (superoxide dismutase), catalase and glutathione, said Dr. David Systrom, director of the Cardiopulmonary Exercise Laboratory at Massachusetts General Hospital in Boston.

Which leads to one of the hottest questions in exercise research: Should athletes take extra antioxidants, particularly vitamins C, E and beta-carotene?

Some data suggest that performance and muscle recovery are enhanced with the supplements. But other data suggest that "anti-oxidants can become pro-oxidants - in other words, free radicals - when taken to excess," said Systrom. "Nobody knows where to draw the line."

Send your questions to foreman@baltsun.com.

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