Scientist warns of Covid’s insidious breath of infection

Ventilation and germ-killing ultraviolet light are the another frontier in the war against Covid, warns university expert

Professor Lidia Morawska, Director, International Laboratory for Air Quality and Health at Queensland University of Technology. Picture- Supplied.

In some ways, Lidia Morawska is an unlikely frontline worker in the COVID-19 pandemic. She does not don personal protective equipment and tend the sick, nor is she in a race against time to develop a vaccine.

However, the Queensland University of Technology physicist and atmospheric scientist, who was named a lifetime achiever in The Australian’s Research 2020 magazine, is engaged in a fierce tussle to have authorities publicly acknowledge the role of airborne transmission in spreading the highly infectious virus.

Coughs, sneezes and other emphatic expulsions of breath are well-known dangers, as is touching virus-contaminated surfaces. But airborne transmission refers to much finer droplets — the aerosols expelled via normal respiration, speaking and singing.

Professor Morawska, director of QUT’s International Laboratory for Air Quality and Health based in the School of Earth and Atmospheric Sciences, is among those campaigning for the recognition of airborne spread as the “third route” of infection.

The implications of taking action “are such that in addition to all the measures advised so far, building engineering measures have to be added, and in particular, good ventilation,” Professor Morawska says.

Read more: The Australian’s 2020 Research magazine

“This is something that we actually need to start changing now to be gradually implemented.”

In July, a commentary she wrote with medical professor ­Donald Milton and backed by 239 scientists from 34 countries was published in the Clinical Infectious Diseases journal, appealing to national and international authorities to take note.

It prompted questions to the World Health Organisation, which advises physical distancing of 1m, wearing a fabric mask if that is not possible, and recommends precautions where airborne transmission can happen — for example, where medical procedures generate aerosols.

Addressing the issue of more general airborne transmission in July, WHO’s technical lead for ­infection prevention and control Benedetta Allegranzi acknowledged there was emerging evidence of airborne transmission.

“The possibility of airborne transmission in public settings — especially in very specific conditions such as crowded, closed and poorly ventilated settings that have been described — cannot be ruled out,” Dr Allegranzi said.

A couple of months ago, it ­appeared briefly as if the US Centres for Disease Control and Prevention was getting on board with a new message.

“There is growing evidence that droplets and airborne particles can remain suspended in the air and be breathed in by others, and travel distances beyond 1.8m (for example, during choir practice, in restaurants, or in fitness classes),” the September 18 CDC advice said. “In general, indoor ­environments without good ventilation increase this risk.”

However, the advice was retracted within days, with the CDC claiming it had been “a draft” posted in error, that recommendations about airborne transmission were being updated, and that “updated language” would be posted.

Professor Morawska says no one really knows what happened at the CDC, but she assumes it was an internal battle.

“The wording of what was first posted was perfect,” she says. “We basically celebrated. So it means that there is a faction there which wants this to be put, but there are other forces which don’t and that’s why they retracted.”

Professors Morawska and Milton said in their commentary that while the evidence for aerosol transmission was “admittedly incomplete … it is similarly incomplete for the large droplet and fomite (surface) modes of transmission” as well.

There have been other Morawska-led papers, including one published recently in Environment International whose co-authors included UNSW respiratory physician and epidemiologist Guy Marks, arguing that while uncertainties remained “regarding the relative contributions of the different transmission pathways … existing evidence is sufficiently strong to warrant engineering controls targeting airborne transmission as part of an overall strategy to limit infection risk indoors.”

Measures to minimise the risk include effective ventilation such as supplying clean outdoor air and minimising recirculating air, “particularly in public buildings, workplace environments, schools, hospitals, and aged-care homes”; supplementing that with “airborne infection controls such as local exhaust, high efficiency air filtration, and germicidal ultraviolet lights”; and avoiding overcrowding, particularly on public transport and in public buildings.

In fact, the CDC did update its language, advising on October 5 that while COVID-19 most commonly spreads during close contact … (it) can sometimes be spread by airborne transmission”. It’s a concession, but not enough for Professor Morawska.

There is no change in the WHO advice. Nor is there any change in Australia’s official advice. Asked about the CDC’s ­September 18 announcement, Australia’s Deputy Chief Medical Officer Nick Coatsworth said: “I wanted to make sure that people were very clear, that … the Infection Control Expert Group, the AHPPC (Australian Health Protection Principal Committee), and federal and state health departments have all recognised the ­important and growing role of ­aerosols in the transmission of COVID-19. We continue to look at the evidence on a daily basis.”