‘Watching brief’ on airborne COVID-19

The World Health Organization (WHO) has acknowledged growing concerns surrounding the airborne transmission of the coronavirus, following the publication of an open letter addressed to the Geneva-based agency, but says more evidence is still required.

Since the beginning of the pandemic, the organisation has advised that the virus is primarily spread through large respiratory droplets – that quickly sink to the ground when expelled from the nose and mouth.

But a number of research studies have now highlighted the potential for the virus to spread via micro-particles that remain suspended in the air.

“The possibility of airborne transmission in public settings – especially in very specific conditions, crowded, closed, poorly ventilated settings that have been described, cannot be ruled out,” said the WHO’s technical lead for infection prevention and control, Benedetta Allegranzi, during a virtual press conference.

“However, the evidence needs to be gathered and interpreted, and we continue to support this,” she said.

The WHO’s technical lead on the COVID-19 pandemic, Maria Van Kerkhove, said the agency would publish a scientific brief summarising the state of knowledge on modes of transmission of the virus in the coming days.

“A comprehensive package of interventions is required to be able to stop transmission,” she said.

“This includes not only physical distancing, it includes the use of masks where appropriate in certain settings, specifically where you can’t do physical distancing and especially for healthcare workers.”

Speaking at an official briefing, Australia’s Deputy Chief Medical Officer Dr Nick Coatsworth was questioned about airborne transmission of COVID-19 and the open letter sent to the WHO.

“Let me just put a little word of caution on that particular comment of aerosolisation,” he said. “We know that you can find virus in the air around someone who is infected, but those tests are largely done in laboratory conditions. We do not necessarily know the implication of that, and how readily that means the virus is going to be spread beyond the 1.5 metres that we recommend people to socially distance.

“We’ve got to remember that the basic reproductive number is only 2.5 and that is more consistent with viruses that the primary mode of spread is contact and droplet, rather than airborne, highly infectious viruses like the chicken pox virus, or like the measles virus.

“We will continue to maintain watching brief on that, but there is no proposed change to the recommendations at the moment.”