You can cut your risk of contracting the flu or other respiratory viruses by as much as 80 percent by wearing a mask over your nose and mouth, according to a new study.

"This is the first clinical trial to show a positive effect of masks on preventing the transmission of respiratory viruses," says Raina MacIntyre, an epidemiologist and head of the School of Public Health and Community Medicine at the University of New South Wales in Sydney, Australia, and lead author of the study published today in Emerging Infectious Diseases, the journal of the Centers for Disease Control and Prevention (CDC) .

The U.S. has been stockpiling face masks to distribute to people in the event of a deadly bird flu or other viral outbreak, but MacIntyre says that until now clinical evidence that they're effective has been thin. She says this study shows they could limit the spread, which is crucial given that it could take up to six months for scientists to roll out vaccines and drugs targeting the responsible virus. 

During the winters of 2006 and 2007, MacIntyre and her team tested the effectiveness of masks on 286 adults (mosty parents) in 143 households in Australia. They split participants into three groups: one in which participants wore surgical masks (used in hospitals), another in which members wore a mask known as a P2 that's specially designed to filter out water droplets containing viruses, and, finally, one in which subjects did not don cover-ups.

All of the participants were initially healthy but at risk for catching viruses from their children, who had documented cases of respiratory illness. The researchers found that, after a week, the non-mask wearers were four times more likely to catch a variety of viruses, including the common cold and flu, than those who wore them properly (meaning they strapped them on whenever they happened to be in the same room as their sick children). The masks appeared to be equally effective.

The U.S. has already stockpiled 51,794, 600 surgical masks and 105,873,370 N-95 masks (similar to the P2 variety used in the study), according to CDC spokesperson Von Roebuck. He notes that each state has its own supply, which the feds will augment if necessary.

For those of you who are interested, surgical masks (made of paper) can be purchased at most local pharmacies for less than a buck, while N-95's (a paper/fabric combination) are available at pharmacies or online for as little as six dollars a pop.

Recent reports underscore the fact that avian flu, the bird virus that could potentially mutate to cause a major epidemic in humans, is an ongoing threat. Just today, China announced the H5N1 strain of avain flu claimed its fifth victim there this month -- an 18-year-old man in the southwestern Guangxi province, according to Reuters.

Image credit © Smith