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Health Sense

Cold comfort

Think you know how to avoid the sniffles? Maybe not

By Judy Foreman
December 8, 2008
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If there's any good news about the common cold, it might be this: You don't have to stop kissing your sniffling loved one's lips just to avoid catching their colds. But you probably will want to stop holding hands.

That insight comes from research into the more than 100 viruses, called rhinoviruses, that cause the common cold. The more researchers learn about these viruses, the more it challenges our common assumptions about how colds spread - sneezing, for example, does not seem to be as important a route of transmission as touching. With time and luck, this knowledge could lead to better ways of preventing colds.

Rhinoviruses infect the lining of the nose. But surprisingly, these viruses don't live in saliva, says Dr. J. Owen Hendley, a leading rhinovirus specialist and professor of pediatrics at the University of Virginia School of Medicine. The lining of the nose "is a different form of epithelial tissue from the lining of the mouth and throat," he says. And the cold virus, having come from the nose, does not fare as well in the dissimilar environment of the mouth.

Colds typically spread when virus-laden mucus from a sick person's nose gets onto the fingertips of a well person who then rubs his own nose or eyes. In short, says Hendley, that means that "kissing is okay, but hand holding is not."

Viruses also go from the tear ducts down into the nose, says Dr. Diane E. Pappas, an associate professor of pediatrics also at the University of Virginia. And it's almost impossible to refrain from touching your eyes and nose. "We touch our eyes and nose multiple times an hour," she says - whether we know it or not.

Usually, the fingertips get contaminated from directly touching the sick person, but there's growing evidence that cold viruses can live for at least a day on surfaces such as doorknobs, telephones, countertops.

Scientists disagree about how easily cold viruses are transmitted by coughing and sneezing, and they cite data to support their position. Dr. Kimon Zachary, an infectious disease specialist at Massachusetts General Hospital, contends that cold viruses "can be transmitted by sneezing on someone," though touch is the more common route. Unlike viruses such as chicken pox that can be spread through the air across a room, the cold virus droplets in sneezes and coughs only travel 3 feet, he says.

Hendley, on the other hand, says, "I don't think the rhinovirus spreads through the air" at all.

Whoever is right, there's no harm in asking people with colds to cough or sneeze into their elbows (not their hands) and in your trying to stay out of the line of fire. If you're sick, throw out your own used tissues.

And it's best to "avoid contact with infected clothing - people still wipe their noses on their shirts," says Dr. Martin Hirsch, an infectious disease specialist at MGH. [Parents: This means washing your hands after you handle your sick kid's clothes.]

Besides endless hand washing, there is one way to kill viruses on your fingertips before you spread them to your nose and eyes. It's iodine - but you probably don't want to go there. Data show that iodine does block viral transmission from drippy-nosed kids to mothers' hands. But it turns hands brown and dries out the skin, said Hendley.

As for those increasingly popular alcohol-based sanitizing gels, sorry, but they may not measure up to plain soap and water. "Rhinoviruses like alcohol. They think it's tasty," says Hendley. For whatever reason, adds Zachary of MGH, "cold viruses are not as susceptible to alcohol-based hand disinfectants as other viruses and bacteria."

And what of the common assumption that the same nasty cold virus can get passed back and forth endlessly within a couple or family? Not true. Most of the time, the next round of colds is because of a new virus.

But if you find that you are recovering from a cold, only to feel sick again, it does not necessarily mean a new virus is at work. "Some cold viruses can be biphasic," says Hirsch, which means that the sufferer can feel sick, then feel better, and then feel sick again - all with the same viral infection. In addition, other microbes, including bacteria, can cause secondary infections such as sinusitis and ear infections.

It may help to know that the time of greatest infectivity is when the sick person is producing the most nasal mucus. Typically, that period lasts three days. If you can manage superb hygiene for those three days, you may not get sick. But you can't necessarily count on the three-day limit; sometimes people shed virus for up to three weeks, warns Hirsch.

The incubation period for rhinoviruses is a day and a half to two days - so if you've been exposed but don't start getting symptoms within two days, you probably have escaped.

Sadly, there are no vaccines against the common cold - there are simply too many viruses that you'd have to be vaccinated against. But researchers' greater understanding of how the virus spreads holds hope for more effective prevention. As consumers get more refined information on how the virus spreads, everyday habits - starting with when it's most important to wash your hands, or the best way to disinfect surfaces - will adjust accordingly, with greater prevention the outcome.

For now, consumers are left with treatments of uncertain efficacy. Many people swear by zinc-based products, but doctors are unconvinced of their value. Gargling with salt water can make a sore throat feel better and nasal lavage with salt water can provide mild symptomatic relief.

Better antiviral drugs for the common cold are nowhere in sight. "Antiviral medications are more difficult to make than antibacterials," says Zachary of MGH.

So back to the good news: Once you become immune to a particular strain of rhinovirus, you're probably immune to that strain forever. But with more than 100 strains, if you get two colds a year, it takes 50 years to acquire immunity to all of them.

In the meantime, wash your hands a lot if your loved one has a cold, and don't worry about the occasional kiss on the lips.

Judy Foreman can be reached at foreman@globe.com.

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