If you’re worried about catching the flu, a facial mask helps, but there is little use for a mask outdoors where the risk of contagion is virtually nil. I keep seeing photos of poor citizens in Mexico City walking around with masks, which does virtually nothing to prevent contagion, but succeeds in keeping people estranged and frightened of each other. The only place you might want to use a mask is indoors, in a closed environment such as stores, planes, trains, etc. As of this writing the hysteria over flu has died down, and people are now focusing again on the economy, celebrity gossip, or crime.
The Centers for Disease Control and infectious disease experts recommend if you’re a health care worker and presumably anyone who really wants better protection than a surgical mask against airborne transmission of flu, SARS, etc. you should only settle for masks that meet the n95 rating. These masks filter out at least 95% of airborne particles labeled “most penetrating” size of 0.3 microns. Don’t forget too that the fit of the mask is also very important; if you can breathe around a mask that isn’t hugging your face, no filter is going to help much.
If you want to stock up in preparation for a possible new outbreak you can buy n95 masks from Alpha Pro Tech ($80 for 35 masks and a respirator). Better still, it may be equally wise to wash your hands after suspected contact with a sick person.
Unfortunately, another epidemic of flu is probable in a few months. Whether it will be a relatively mild illness as the present strain appears to be, or a more virulent one, no one at this point seems to know. Keep posted, but don’t panic. For my part, I’m not rushing out to buy a mask just yet.