They are fear soothers and even fashion statements.
Surgical masks seem to be the only tangible step worried people think they can take against the new, highly contagious disease spreading through Asia and into North America.
Whether simple cloth swaths or sophisticated respirators -- sometimes in basic black or with cartoon characters -- they have become commonplace in Hong Kong and other Asian cities faced with severe acute respiratory syndrome, or SARS.
With a growing outbreak in Canada's largest city and more cases emerging in the United States, health authorities report a deluge of questions about whether the stuffy, uncomfortable masks will help.
The answer is no -- unless you are in direct contact with someone already infected.
Medical experts believe SARS is spread by droplets from the sneeze or cough of an infected person. That means people in direct contact with SARS victims are at risk, not the public at large.
They recommend doctors and nurses, loved ones and others who deal with SARS cases should have respirator masks that filter out contaminants, while common surgical masks can contain droplets from those already infected.
Anyone else just doesn't need a mask, they say.
Dick Thompson, a spokesman for the World Health Organization, noted a run on masks could cause a shortage for those who need them -- the sick and those treating them.
"People buying them so they feel comfortable riding the subway doesn't make a lot of sense," Thompson said. "We're just not going to encourage silliness because we don't want to see a shortage of masks."
Last month, Ontario health officials bought all the high-grade surgical masks available in Canada to protect medical workers.
Toronto has the largest SARS outbreak outside of Asia. Authorities here have cut access to hospitals and told anyone exposed to SARS to stay home in quarantine for 10 days. All hospital staff, including security guards, must wear masks and other protective gear.
The measures appear to be helping. Canada's 200 suspected cases are all linked to sources that originated in Asia or one local hospital that first treated the illness. Ten people in Canada have died.
Few people wear masks on Toronto's streets, heeding the advice of Canadian health officials who say frequent hand-washing is more important.
Besides, wearing a mask "is not particularly pleasant," said Dr. James Young, the Ontario commissioner of public safety.
"There's been a lot of complaints about people developing allergies to the mask and feeling very confined in them."
WHO recommends health care workers wear N95 respirator masks -- the same kind used for dealing with tuberculosis. Designed to block 95 percent of contaminants, they seal on the face and have a filter to breathe through.
Several companies produce N95 masks, which can be bought for about $15.75 for a box of 20. Simpler masks can catch droplets but offer little protection from germs.
In Hong Kong, with almost 1,000 SARS cases and more than two dozen deaths, masks are everywhere.
Authorities there say one reason is the higher population density.
In some cases, the SARS outbreak has made masks a kind of Hong Kong fashion statement. While many people wear plain green or blue masks, some have white surgical masks beneath another patterned mask -- say polka-dot, checked, animal print, or classic black.
Esther Li, a 20-year-old Hong Kong saleswoman, said she wore a Hello Kitty mask, but stopped when friends laughed at her.
"I wore it because it was beautiful," Li said. "Hello Kitty was wearing a pink dress, so I put on a pair of blue jeans to make a nice contrast."