Coronavirus infection could take the airborne route

An infectious diseases expert has raised the possibility that the coronavirus could be transmitted via airborne particles.

An academic paper said it would be ‘prudent’ to assume the virus that causes COVID-19 may have airborne transmission.

An infectious diseases expert has raised the possibility the corona­virus could be transmitted via airborne particles, with asymp­tomatic carriers of COVID-19 just as likely to pass on the disease as those with symptoms.

In a paper published in the journal of Public Health Research & Practice, the head of the biosecurity program at the UNSW’s Kirby Institute, Raina MacIntyre, said it would be “prudent” to ­assume the virus that causes COVID-19 may have airborne transmission, as was the case with SARS.

“SARS was documented to be spread by airborne, droplet and contact routes,” Professor MacIntyre wrote in the paper.

“A report of transmission of COVID-19 from floor to floor of a building in Hong Kong has raised questions about long-range aerosol transmission.

“(The novel coronavirus) is a respiratory virus, with higher viral loads in the lower respiratory tract compared to the upper, consistent with the possibility of airborne transmission. It is therefore prudent to assume that transmission may be by contact, droplet and possibly airborne modes.”

The theory goes against the advice of the Australian government and most international experts that COVID-19 is spread via droplets when an infected person sneezes or coughs. There are also questions surrounding the infectiousness of people who do not exhibit symptoms, even if infected.

Japanese researchers have estimated that as many as 90 per cent of cases are undetected.

Professor MacIntyre said in the paper that data showed “the viral load detected in an asymptomatic person was similar to that in symptomatic people”. “This means that asymptomatic cases may be as likely to transmit infection as symptomatic ones,” Professor MacIntyre said. “Further, the highest viral load is early in the illness when symptoms are mild.”

The average time from infection to the first display of symptoms was between five and nine days, the paper said. That meant there was “substantial opportunity for community infection” before a virus carrier had sought medical attention.

Professor MacIntyre has predicted that Australia may have a higher death rate from COVID-19 than China because of our ageing population. “With an ageing population and a more severe illness in older people, Australia may see a proportionately greater morbidity and mortality impact than China,” she writes in the paper.

Professor MacIntyre said travel bans were effective in slowing the spread, and once travel bans were lifted, there was likely to be a surge of cases worldwide. “Sites where young people congregate, such as schools, universities, sporting and entertainment venues, would be sites of more intense transmission, and epidemics in aged-care facilities may also occur,” the paper said.

“The use of community volunteers and alternative sites for contact quarantine and case isolation may need to be considered during a pandemic.”