Surgical masks offer little protection against flu - expert

Surgical masks used for decades in hospitals offer little protection against air-borne viruses, says Professor Raina MacIntyre.

Health workers involved in any frontline response to pandemic flu should instead be wearing a more expensive alternative, she says.

"For healthcare workers, really they should be using N95 respirators because surgical masks do not offer significant protection," says Prof MacIntyre, who lead the China-based study.

"... Definitely in high-risk settings like emergency departments or a respiratory ward I would say a N95 should be the standard of care."

A N95 respirator looks similar to a surgical mask though it fits tightly to the face, and it has thicker mesh designed to filter 95 per cent of particles from the air.

Surgical masks were originally designed to prevent contamination of wounds during surgery, but they have become part of health workers' protective equipment and are used during treatment of people with pandemic flu.

A world-first comparative trial of the different masks' effectiveness against air-borne viruses was conducted in Beijing during the Chinese capital's most recent winter flu season.

Prof MacIntyre says almost 2,000 doctors and nurses took part, and they were split into groups who wore either N95 respirators, standard surgical masks or nothing.

"These are healthcare workers working in respiratory wards and emergency departments, and quite high-risk settings where they get exposed to a lot of bugs over the winter," Prof MacIntyre says.

"What we found was that the N95 masks were protective against ... clinical respiratory illness and laboratory-proven viral infections, but the surgical masks were not."

Monitoring after four weeks showed almost ten per cent of the workers who wore no face masks fell ill, while for those who wore surgical masks the rate was almost seven per cent.

For those who wore the N95 masks, the illness rate was about four per cent.

Prof MacIntyre presented the results of the research at the Interscience Conference on Antimicrobial Agents and Chemotherapy, in San Francisco, this week.

The research is expected to meet some resistance from health authorities, and possibly health workers, as the N95 respiratory masks can cost five to ten times the price of surgical masks.

Each worker must also be fitted with an N95 mask, a process that must be repeated annually, while some have complained the masks are too restrictive to work in.

"It is very political and it's not a very popular finding," Prof MacIntyre says.

"(But) this the first trial that really compared N95 respirators with surgical masks. There are guidelines all over the world that recommend surgical masks in various situations for health care workers, but there has been no evidence until now."

Prof MacIntyre is Professor of Infectious Diseases Epidemiology and Head of the School of Public Health and Community Medicine at the University of NSW.

She also sits on the Scientific Influenza Advisory Group to the Chief Medical Officer of Australia.