EMERGENCY PREPAREDNESS MEDICAL SUPPLIES
FOR A PANDEMIC
MEDICAL MASK INFORMATION:
Do Surgical Masks Stop SARS?
By Jon Cohen
Posted Monday, April 7, 2003, at 5:41 PM ET
Masks: a poor prophylactic
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.
The University of Cincinnati's Sergey Grinshpun has studied N-95 respirators
and says it all comes down to "collection efficiency." N-95s
made by different manufacturers have different collection efficiencies
below the .3 cutoff. In other words, one company's mask, if properly
fitted, might filter out 92 percent of coronaviruses, while another
might catch only 50 percent.
"It seems to offer better protection than nothing," Grinshpun
says. And he notes that viruses often travel on top of larger carrier
molecules—like globs of mucus—making it easier to filter
them. That's why CDC Director Julie Gerberding last week noted that
covering your face with a T-shirt might help if you come in close contact
with an infected person.
To efficiently protect yourself from coronaviruses, you would need
to wear a full-faced mask with a high-efficiency particle air filter.
But such HEPA filter masks cause what Grinshpun calls "quite a
discomfort" in short order.
Any mask clearly wards off one bug: fear. Confoundingly, the sight
of so many people wearing masks also spreads fear. And there's no measure
of collection efficiency or fit factors that can help humans out of
Simple surgical masks can reduce the spread of bacteria in aerosols. Apart
from protecting the wearer from splashes in the mouth with body fluids,
they are intended to protect others from the wearer's oral and nasal bacteria.
They are not designed to protect the wearer from inhaled particles.
Viral particles are far too small to be effectively filtered by the fibers
of a regular surgical mask. Thus, a mask wearer would not be
less likely to catch a viral disease than someone not wearing a mask.
However, an already infected person wearing a mask may slightly reduce
his chances of infecting others, as it may catch droplets of fluid expelled
during sneeze or cough.
The NIOSH N95 standard mask is able to protect the wearer from viral
particles in aerosols and airborne liquid droplets. Another benefit
of masks, even ones permeable to viruses, is to remind the wearer not
to touch his face. Direct skin contact after touching a surface with
viruses on it (termed a fomite) may transfer viruses which are not typically
A surgical mask will trap some particles but is much less effective
than a mask designed for this purpose.
Find all FDA-cleared surgical masks and surgical N95 respirators. The
FDA’s website lets you search for medical devices that FDA has cleared
or approved, including personal protective equipment.
Search for all FDA-cleared surgical masks
for all FDA-cleared surgical N95 respirators
NOW YOU KNOW A LITTLE MORE ABOUT WEARING SURGICAL MASKS IN A PANDEMIC!!!
Stake Member Input:
Hi, interesting stuff, if a little disappointing that they don't
protect better from the viruses, but I thought the reason we wanted to
have masks in our emergency preparedness stuff was to filter out dust
when we need to clear out buildings or digging for people trapped and
that sort of stuff. The same reason we want to be sure to have a good
pair of work gloves and sturdy shoes handy. Tony always had some masks
on hand when we were helping him in his cabinet shop to use when there
was lots of sawdust. Funny I wasn't even thinking of protection from viruses!