Face masks may guard against swine flu

STANFORD , Calif., May 21 (UPI) -- Face masks are effective at filtering out aerosol transmission of influenza and may be effective against the H1N1 virus at home, U.S. researchers found.

Lawrence M. Wein and Michael P. Atkinson of Stanford University constructed a mathematical model of aerosol transmission of the flu to explore infection control measures in the home.

The model predicted that the use of face protection including N95 respirators -- which fit tight around the face and are often worn by construction workers -- and surgical masks -- these fit looser around the face and are often worn by dental hygienists -- are effective in preventing the flu.

The filters in surgical masks keep out 98 percent of the virus. However, only 30 percent of the benefits of the respirators and masks are achieved if they are used only after an infected person develops symptoms.

"Our research aids in the understanding of the efficacy of infection control measures for influenza, and provides a framework about the routes of transmission," the study authors said in a statement.

The findings are published in the journal Risk Analysis.