Two arrested for selling expensive flu masks in Mexico City

Do Surgical Masks Stop SARS?By Jon Cohen

The dramatic photos of surgical-masked people walking the streets of Asian cities hit by severe acute respiratory syndrome pose the question: Do the masks offer them any meaningful protection against the disease?

Viruses, including the coronavirus that scientists believe may be the cause of SARS, are so tiny that they can easily pass through such barriers. Several studies even have shown that surgical masks fail to prevent transmission of the much larger mycobacterium tuberculosis, which causes TB. While the U.S. Centers for Disease Control and Prevention advises that people who have SARS wear these masks, they do not even recommend them for people in contact with those patients unless the infected person can't wear one. Wearing surgical masks outdoors, where virus-laden particles easily disperse, has even less value.

CDC does advise health-care workers working with SARS patients to wear a special mask called an N-95 respirator. But even these masks offer limited protection from coronaviruses. The name of the mask says it all. The "95" means the mask, if properly fitted—and that "fit factor" presents a big if—can filter out particles down to .3 microns 95 percent of the time. (A human hair is roughly 100 microns in diameter.) Human coronaviruses measure between .1 and .2 microns, which is one to two times below the cutoff.