Researchers at Mt. Sinai Hospital have shown that the flu virus spreads more readily in cold, dry air, which could be because the virus lives longer in the cold and is also more difficult to clear from the throat. Guinea pigs used in that study transmitted the flu more frequently at cool temperatures than they did at moderate ones, yet there was little difference in the guinea pigs' ability to fight infection in the cold. Similarly, humidity levels above 80 percent nearly shut down the flu's infectious abilities.1
From One Place to Another
Humidity may well act like a drag chute on cold and flu viruses. Often you fall victim to a virus when an infected person sneezes or coughs. Sneezes can travel 15 feet and propel some 40,000 potentially infectious droplets. That's why homes, offices, and classrooms are easily contaminated.2 High humidity, though, cuts down this distance, so viruses are suspended for less time in warm, heavy air than they are in cold, dry air—and are less likely to be inhaled.The other common way to catch cold or flu is through contact with contaminated surfaces, whether that's an infected person or an object they've touched or coughed on. Solid surfaces transmit the virus more readily than porous surfaces, such as towels and upholstery, do.
Feeling Sick Inside
Once cold or flu viruses do get into your mouth, eyes, or nose, both work quickly. Rhinovirus, the most common type of cold virus, attaches itself in the respiratory tract within 15 minutes of contact, and symptoms often appear eight to 10 hours later.3 The flu's incubation period can be longer, two to five days, but when it hits, it hits hard and fast. Fever and pronounced muscle weakness are telltale signs of flu but nearly unheard of for a cold.Fighting Back
There truly is no cure for the common cold. Hand washing and avoiding infected people are your best defense, but not everyone who carries a cold virus shows symptoms, so even those who appear healthy can be contagious—including you!The same advice goes for potential flu sufferers, who can improve their odds by getting a flu shot in the fall. (You still could get sick, however, from a flu strain not covered by the vaccine.) Once infected, you might consider an antiviral medication such as Tamiflu® or Relenza® to relieve symptoms. Both are best taken within two days of onset. Because cold and flu are caused by viruses, antibiotics are unlikely to help you.
1 Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature. PLoS Pathogens. Oct 2007.
2 Characterization of Infectious Aerosols in Health Care Facilities. National Institutes of Health. American Journal of Infectious Control. Aug 1998.
3 Rhinovirus: An Unstoppable Cause of the Common Cold. The Science Creative Quarterly. Aug 2004.
