Prevention

Become a bad host for cold and flu viruses.
Wash up.
A study in 2001 at Ryerson University, in Toronto, found that people who washed their hands at least seven times a day got one-fourth as many colds as those washing less often. If you're not near a sink, use antiseptic wipes or waterless cleaners, such as Purell, which can cut your risk of getting a cold in half, says Charles Gerba, Ph.D., a professor of environmental microbiology at the University of Arizona at Tucson and a coauthor of The Germ Freak's Guide to Outwitting Colds and Flu (www.amazon.com HCI, $12).

Keep your hands clean by avoiding well-handled objects like the pens at banks and restaurants (bring your own). Wipe down shared items, like phones and grocery carts, with a germ killer, such as Clorox Disinfecting Wipes. "Influenza and cold viruses can live from two hours to three days on surfaces," Gerba says. In high-traffic restrooms, faucet handles are often teeming with germs, he says. So try to avoid them, and carry your own disinfecting wipes.

When a family member is sick, clean communal items like telephones and remote controls frequently, and give the sick person Kleenex antiviral tissues, which make used tissues less contagious by killing the virus.

Get a flu shot.
The vaccine, which every year protects you from the season's three predominant flu strains, is up to 90 percent effective at preventing illness, according to the Centers for Disease Control and Prevention (CDC). Even if you've already had the flu, you should get a shot—although you're immune to a strain once you've had it, the vaccine will still protect you from the other two. Pregnant women should definitely get immunized, because the flu can cause serious complications and possibly jeopardize the health of an unborn baby.

If you hate needles or there's a vaccine shortage in your area, consider FluMist, a prescription nasal-spray vaccine. Made from a live virus (not a dead one, as the regular vaccine is), it has a few more side effects, like a runny nose and a sore throat, which last for less than a week. But for most healthy people between ages 5 and 49, the mist is fine.

Boost your immunity.
Sleep seven to eight hours a night, eat well, and exercise regularly. Avoid smoking and extremely vigorous exercise (like working out for more than two hours a day), which can depress your immune system. And consider echinacea. Despite a much publicized July report in the New England Journal of Medicine pronouncing it ineffective at preventing infection from rhinoviruses, the cause of colds, some experts remain positive. "The dose used for this trial was less than one-third the internationally recognized dose," says Mark Blumenthal, founder and director of the American Botanical Council, in Austin, Texas, a nonprofit organization that reviews information about herbal medicines. Most of the clinical trials on echinacea show it helps boost immunity, says Blumenthal, who still takes the herb when he feels a cold coming.