WASHINGTON Face masks may do little to prevent infection during an influenza pandemic, but wearing them might help comfort people in crowds, the U.S. Centers for Disease Control and Prevention said on Thursday.
And people who must care for someone else who is sick during a pandemic should wear a respirator -- a specially designed, form-fitting mask, the CDC said.
It admitted that no one has done the research to show what good, if any, a surgical-style mask would do in stopping the spread of a virus.
Experts say a flu pandemic is inevitable. No one can say when it will come, or what strain of virus, but there were three flu pandemics in the last century.
The chief suspect is the H5N1 avian flu virus infecting flocks of birds across Asia, parts of Europe and Africa. It rarely infects people but has killed at least 172 of the 291 people whose infection was confirmed by the World Health Organization.
If it develops the ability to pass easily from one person to another, it would infect tens of millions of people and could kill millions, WHO says. A good vaccine would take months to manufacture.
Many experts have been asking questions about whether masks might help people protect themselves and might be worth stockpiling now.
The CDC's answer? Maybe.
"We also know that many people may choose to use masks for an extra margin of protection even if there is no proof of their effectiveness," CDC director Dr. Julie Gerberding told reporters.
"If people are not able to avoid crowded places, large gatherings or are caring for people who are ill, using a face mask or a respirator correctly and consistently could help protect people and reduce the spread of pandemic influenza."
Other measures already recommended by the CDC and WHO include hand washing, staying away from other people and discouraging crowds.
Some experts have argued that wearing a face mask might give people a false sense of security.
Face masks might be useful in the following instances, the CDC said:
-- If people have the flu and think they might have close contact with other people -- within about 6 feet.
-- If they live with someone who has the flu symptoms or will be spending time in a crowded public place and thus may be in close contact with infected people.
-- If people must be in a crowd.
-- People should use a respirator mask if they must be in close contract with someone who is ill.
"Face masks are not designed to protect people from breathing in very small particles, such as viruses," said Dr. Michael Bell, an infection control expert at CDC.
"Rather, face masks help stop potentially infectious droplets from being spread by the person wearing them. They also keep splashes or sprays from coughs and sneezes from reaching the mouth and nose of the person wearing the face mask."