TORONTO - Should people consider wearing medical masks to reduce their risk of infection during a flu pandemic? The U.S. Centres for Disease Control says the answer to that question is a very qualified maybe.

The Atlanta-based health agency issued interim recommendations on the use of medical masks and respirators by the public on Thursday, saying people should try first to lower their risk of being infected by avoiding crowded conditions whenever possible.

People who have to go into crowded settings "should consider" using surgical masks and should limit their time in these settings, the guidelines say.

If people need to be in contact with a person sick with influenza, they should consider using a respirator - the technical term for the moulded masks frequently used in industrial workplaces and sometimes in hospitals.

The lead spokesperson for the policy statement said this doesn't mean the CDC is urging people to go out and stockpile surgical masks and N-95 respirators.

"The main thing to do is avoid exposure altogether and stay home and stay away from crowds," said Dr. Michael Bell, associate director for infection control in the CDC's division of healthcare quality promotion.

"And if you decide that you in addition want to have masks and respirators, I think this guidance helps you understand when you might want to use them. I think it's a nice step in avoiding the need for huge supplies if you realize you only need them in discrete circumstances."

Bell said the CDC had been asked to produce advice for the general public on whether it would be useful to plan to wear masks during a pandemic.

But currently there is little scientific evidence to say whether masks would help people avoid infection.

And experts worry that masks may give people a false sense of confidence and they might let down their guard on measures that may be more effective at preventing infection such as handwashing and keeping one's hands away from one's nose, eyes and mouth.

"One of the reasons that this guidance is written is to really try and get people to only consider these devices under very specific circumstances," Bell said.

"Because we really don't want people wearing them willy nilly and believing that they are somehow not at risk of becoming infected."