Face masks are everywhere in Mexico City as people try to protect themselves from swine flu, the Associated Press says. The government has handed out millions of them. But U.S. officials say there's little evidence that they help to prevent the spread of flu. The U.S. Centers for Disease Control and Prevention has not advised the public to use them. Some experts say masks might even cause harm. This could occur if people who wear them fail to take other precautions such as washing hands often.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
I just returned from Los Cabos, Mexico, two days ago. This part of Mexico had not seen any cases of suspected swine flu while I was there. Despite the widespread news of the swine flu outbreak in Mexico City, on the Baja peninsula there was no immediate concern.
I did not cut my trip short. In the airport, as I was preparing to return home, I saw only five people wearing masks and hundreds not wearing masks. The five appeared to be healthy.
Only one of the five was wearing the mask correctly. Three of them actually had it tied over their noses but open around their mouths.
During the last few days, wearing a surgical mask has become the norm in Mexico City. But it's not clear whether wearing a mask in public will help to protect you from acquiring flu. Scientific proof is lacking, but still the mask might have a positive effect. It could remind the residents of Mexico City to take other precautions that can decrease risk of spreading flu.
The potential downside would be if you believed a mask provided all the protection needed. Then you might be less careful about other preventive measures.
In hospital settings, health care workers use one of two types of masks. The surgical mask is the one you see commonly hanging around the neck of doctors on TV. The other type is called a respirator; the one used most commonly is the N95.
The surgical mask is a loose-fitting face mask that covers the nose and mouth. Face masks worn by an infected person can help stop droplets from getting into the air. They don't protect you from breathing in small particles such as influenza viruses.
The N95 and other respirators can filter out small particles. They must fit tightly against the skin, with full coverage of the nose and mouth. They cost much more than surgical masks.
What Changes Can I Make Now?
The U.S. Centers for Disease Control and Prevention (CDC) has offered some guidance about using masks should we be faced with a flu pandemic. The CDC stresses that masks are only a small part of containing the spread of flu. A combination of actions would be needed in a flu pandemic. For example:
- Wash hands often.
- Keep a distance of at least 6 feet if you have any symptoms of the flu or live with someone who may have the flu.
- Work at home if possible if you or a family member has flu symptoms.
- Avoid crowded places and large gatherings.
The CDC suggests that you consider wearing a surgical mask if:
- You are sick with the flu and will have close contact with other people (within about 6 feet)
- You live with or have recently visited someone who has the flu symptoms
- You can't avoid spending time in a crowded public place during a flu pandemic
The CDC recommends considering using an N95 or other respirator during a flu pandemic if:
- You are not sick now AND
- You expect to be within about 6 feet of people who are known or believed to have pandemic flu
Don't rely on the respirator. Use other precautions too. Limit the amount of time you are in close contact with these people.
Studies have shown that most people do not use masks and respirators consistently with proper fitting. This is essential if you do choose to wear one.
What Can I Expect Looking to the Future?
Within the next week, we almost surely will know if this is going to turn into a flu pandemic. The good news is that we are now much better prepared because of prior experience with SARS and the bird flu. Public officials are mobilizing to try to contain the disease.
