Hospital infection control guidelines worldwide have long recommended surgical masks for infections spread by droplets, but UNSW research challenges that approach.

The longstanding belief that a surgical mask provides adequate protection against infections spread by droplets has been turned upside down by new research that finds respirators do a better job.

UNSW Professor of Infectious Disease Epidemiology and PLuS Alliance Fellow Raina MacIntyre and her team have conducted the largest body of work internationally on masks and respirators, which was a finalist for the 2017 Eureka Prize in Infectious Diseases.

Hospital infection control guidelines worldwide recommend surgical masks for infections spread by droplets, such as influenza, which currently has Australia’s health system under huge pressure.

Professor MacIntyre and team tested the evidence for such guidelines. using data from two large randomised controlled trials involving 3591 subjects in Beijing, China.

The study, published in the journal Influenza and Other Respiratory Viruses and available online, failed to show protection by surgical masks.

“We showed that even for infections spread by droplets, respirators protect better,” Professor MacIntyre said.

Surgical masks are loose fitting, disposable masks that cover the mouth and nose, while respirators are designed to fit closer to the face and to filter 95% of airborne particles.

“This turns upside down the long-held beliefs on infection control. It suggests that transmission of infection cannot be neatly classified as large droplets versus airborne particles.

“Probably infections we believe to be spread by large droplets also have some airborne transmission.”

Guidelines for prevention of influenza are based on the belief that influenza is mainly spread by droplets. However, many studies also show airborne transmission of influenza, and this study adds to the evidence.

The belief that a surgical mask is good enough for infection prevention and that the more purpose-designed respirators are not necessary came to the fore globally during the 2009 pandemic, and again during the Ebola epidemic of 2014, where many guidelines recommended surgical masks.

Drugs or vaccines are often unavailable during serious epidemics, and frontline health workers require protection from masks, respirators and other personal protective equipment (PPE). During the 2014 Ebola epidemic, PPE was the mainstay of protection for doctors and nurses.