workforce
The masking effect
Are surgical masks good enough for protecting
against infection spread by droplets?
By Dallas Bastian
A
study comparing the effectiveness of surgical masks
with respirators has challenged long-held beliefs about
infection control.
A University of New South Wales research team drew from the
data of two randomised controlled trials involving 3591 Chinese
participants to test the efficacy of hospital infection control
guidelines that recommend surgical masks for infections spread
by droplets.
Research lead Professor Raina MacIntyre says the evidence is
now overwhelming that respirators do a better job of protecting
against respiratory infection than surgical masks, and that the
evidence supporting surgical masks is very weak.
While surgical masks are loose fitting and cover the mouth and
nose, respirators are designed to fit closer to the face and filter 95
per cent of airborne particles.
MacIntyre says even for infections spread by droplets, the study
showed that respirators protect better.
“This turns upside down the long-held beliefs on infection
control,” she says, because it suggests transmission of infection
cannot be neatly classified as large droplets versus airborne
particles.
Generally, guidelines recommend that health professionals use
surgical masks to prevent infections spread by droplets, but one
of the major findings of the study was that even for infections
that are presumed to be spread by the droplet mode, a respirator
protected much better than a surgical mask.
“The guidelines are saying if it’s droplet infection, a surgical mask
is fine, but what we showed is that actually a surgical mask doesn’t
even protect against droplet infection.”
MacIntyre says this means that, in practice, infections cannot
be easily categorised into droplet and airborne, and it’s likely that
infections believed to be spread by large droplets also have some
airborne transmission.
She says the issue of putting infections in the boxes of airborne
and droplet plays out in the approach to influenza.
24 | nursingreview.com.au
“The common belief about influenza is that it’s droplet-spread.
There’s already a whole body of research showing that, yes,
influenza is spread by the big droplets, but it is also airborne.
“For example, there was a study in the US where they looked
at the emergency department after a patient with flu had been
in there, and they could isolate full influenza virus in the air, three
hours after the patient had left the emergency department. That
proved that you do get airborne transmission.”
As of July this year, the Department of Health recommended
that residential aged care staff providing direct care to a resident
with influenza, as well as visitors entering the room of a person
with a respiratory illness, wear a single-use surgical mask.
This advice was provided through a practical guide developed
by the Working Group on Influenza Outbreaks in Residential
Care Facilities on behalf of the Communicable Diseases Network
of Australia (CDNA) and endorsed by CDNA at the beginning
of March. The guide noted that P2 respirators protect the user
against aerosols as well as droplets.
It also said insufficient evidence exists to support the use of P2
respirators to further reduce the risk of infections transmitted by
the droplet route.
The authors of this new study, published in Influenza and Other
Respiratory Viruses, say the findings confirm that respirators
should be used to ensure health workers are protected at
the frontline.
“It is time that guidelines reflect the available evidence and that
the safety of health workers is prioritised.”
Their call comes less than a month after the number of deaths
due to influenza in aged care facilities reached 21.
More than 90,000 cases of influenza have been reported this
year, which is 2.5 times the amount recorded in the same period
last year.
The outbreaks prompted Health Minister Greg Hunt to
announce that the government will investigate ways to make the
flu vaccine compulsory for workers in aged care facilities.
Aged Care Minister Ken Wyatt confirmed on Tasmanian radio
that the Australian Aged Care Quality Agency, as part of its review
into the practices of all aged care facilities, will closely look at
its infection control program, including its plans, procedures,
practices and equipment. ■