Really? - The Claim - Flu Viruses Live Longer on Surfaces Than Cold Viruses - Question - NYTimes.com THE FACTS Most people know that cold and flu viruses can contaminate doorknobs, faucets and other surfaces. But for how long? Studies have found that the survival time for both kinds of viruses varies greatly, from a few seconds to 48 hours. The reasons have to do with a number of factors, including the type of surface, humidity and temperature. For example, cold and flu viruses survive longer on inanimate surfaces that are nonporous, like metal, plastic and wood, and less on porous surfaces, like clothing, paper and tissue. Most flu viruses can live one to two days on nonporous surfaces, and 8 to 12 hours on porous surfaces. But a 2006 study found that avian influenza seemed particularly hardy, surviving as long as six days on some surfaces. Cold viruses, however, deteriorate quickly. A study in 2007 found that when objects in a hotel room - light switches, telephones - were contaminated with a cold virus, 60 percent of healthy volunteers picked up the virus when they touched one of the objects an hour later. Eighteen hours later, the transmission rate was cut in half. On skin, cold and flu viruses generally last less than a few minutes, but that can be plenty of time: studies show that most people touch their hands or mouth several times in the course of daily activities - enough to cause infection. THE BOTTOM LINE Flu viruses tend to survive longer than cold viruses. More Articles in Health " A version of this article appeared in print on December 15, 2009, on page D5 of the New York edition.