There are growing concerns the virus behind COVID-19 could be airborne, which could explain its rapid spread around the world.
More than 145,000 people have lost their lives in the past few months to the new disease, for which no vaccine exists and no one - prior to exposure - has immunity.
While the current World Health Organization position is that the virus can only spread through respiratory droplets expelled in coughs and sneezes, researchers are finding evidence it can also persist in the air like measles does, making it much harder to avoid contracting.
Air quality expert Professor Lidia Morawska of the Queensland University of Technology says urgent research is needed into whether SARS-CoV-2 - the name of the virus which causes COVID-19 - is airborne.
"National health bodies responsible for controlling the pandemic are hampered by not acknowledging the research evidence of airborne transmission of viable virus droplets, that was conducted after the SARS 2003 outbreak," she said on Thursday.
As its name suggests, SARS-CoV-2 is related to SARS, the virus which killed hundreds of people in 2003 and caused a global scare before being stopped in its tracks.
SARS was airborne and had a much higher mortality rate than COVID-19, but doesn't appear to have been as infectious. But Dr Morawska says the fast spread of COVID-19 through cruise ships, despite precautions, suggests it too is airborne.
"On numerous cruise ships where thousands of people onboard were infected, many of the infections occurred after passengers had to isolate in their cabins even though hand hygiene was implemented," said Dr Morawska.
"Therefore, the ventilation system could have spread the airborne virus between the cabins... Air transmission research should be undertaken now and its likelihood as a means of spread should be taken seriously with due precautions taken now."
A recent study published in the New England Journal of Medicine found the virus could hang around in the air for up to three hours after being expelled. The WHO dismissed those findings, saying the circumstances needed to get the virus to hang in the air were artificial.
"Aerosols were generated using... a high-powered machine that does not reflect normal human cough conditions," the WHO said in a statement on March 29.
"Further studies are needed to determine whether it is possible to detect COVID-19 virus in air samples from patient rooms where no procedures or support treatments that generate aerosols are ongoing."
PPE like masks and face shields can help prevent droplets being inhaled, but unless they're airtight, would be less effective against an airborne virus. There's also evidence the virus can enter the body through the eyes, which might not be sealed off by a face shield.
The virus is able to travel further than the social distancing recommendation of 2m, Dr Morawska said, as some droplets expelled in coughs and sneezes "evaporate immediately", leaving the microscopic virus able to float in the air.
She said in addition to social distancing, we should:
- increase ventilation of indoor spaces
- use natural ventilation
- avoid air recirculation
- avoid staying in another person’s direct air flow
- Minimise the number of people sharing the same environment
- provide adequate ventilation in nursing homes, hospitals, shops, offices, schools, restaurants and cruise ships.
"Such small droplets can carry their viral content metres, even tens of metres, away from the infected person... Air transmission research should be undertaken now and its likelihood as a means of spread should be taken seriously with due precautions taken now.
"We have already lost valuable time by ignoring this method of spread and we should act on the presumption that COVID-19 is spreading on the air."
The article was published this week in journal Environmental International.