clinical focus
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 .
“ 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 . ■
28 agedcareinsite . com . au