Q and A with epidemiologist Dr Zoë Hyde, from The University of Western Australia’s Medical School.
Given recent transmission of the COVID virus between hotel quarantine rooms in Australia, do you believe there is now clear and compelling evidence for airborne transmission of SARS-CoV-2?
There’s now ample evidence from around the world that COVID-19 is an airborne disease. We’ve seen numerous outbreaks in apartment complexes, public transport, hospitals, choir groups, hotel quarantine, and other places, that can only be explained by airborne transmission. We can say this with certainty, because there was no direct contact between the affected people in these outbreaks. We’ve found the genetic material of the virus in hospital ventilation systems, far away from patients. Scientists have also managed to grow the virus from air samples that were taken several metres away from infected people.
"We’ve found the genetic material of the virus in hospital ventilation systems, far away from patients. Scientists have also managed to grow the virus from air samples that were taken several metres away from infected people."Dr Zoë Hyde
Is the evidence sufficient to warrant the immediate strengthening of Australia’s infection prevention and control guidelines?
Australia’s COVID-19 guidelines are mostly based around contaminated surfaces and what’s called droplet transmission. As the name suggests, these are relatively large droplets that can be produced by speaking, coughing, and sneezing. But we now know that the virus can be spread by much smaller particles called aerosols. These are very fine particles that can be produced by breathing, and which spread through the air like cigarette smoke. Aerosols can drift many metres through the air, and they build up in a room if it’s not ventilated. This is known as airborne transmission, and our current guidelines don’t take this into account. Airborne transmission is far more common than thought, and we need to urgently update the COVID-19 guidelines to reflect this.
In recognition of this, what are the implications for and urgent improvements now needed at quarantine facilities, hospitals, ports, airports, public buildings and public transport?
The most important thing we can do is improve ventilation by letting in more fresh outdoor air. When it’s not possible to open windows, we need to be looking at using air cleaners with HEPA filters to clean the air. We also need to give people better masks. Surgical masks do block aerosols to some extent, but this isn’t really what they were designed for. Surgical masks really only protect against the larger droplets. Instead, we need to give people the type of mask that blocks both droplets and aerosols. These are called P2 or N95 masks. We also need to change hotel quarantine to cabin-style accommodation, separated by open air, like the Howard Springs model.
Current hotel quarantine guidelines don't take airborne transmission of COVID-19 into account.
Does the emergence of more transmissible variants heighten the risk of urgency to act and does it increase the risk of outbreaks continuing to spill over into the community?
The new variants of COVID-19 are particularly dangerous, because people have much higher levels of the virus in their nose and throat. This makes airborne transmission much more likely, because more of the virus builds up in the air. We’ve already started to see more outbreaks in hotel quarantine as the variants have become more common. We need to urgently start following airborne precautions otherwise we’ll see the virus getting into the community more often.
Given the more transmissible variants and issues with hotel ventilation, gaps under doors and shared lifts, are hotels no longer suitable/safe to act as quarantine facilities? Is the ventilation audit of established quarantine hotels enough to ensure the safety of returned travellers, quarantine hotel staff and the community as a whole?
The hotel quarantine system has been an enormously positive thing for Australia. If we didn’t have it, there’s no question that Australia would have a terrible epidemic, just like Europe or America. So we definitely need to keep the hotel quarantine system, but we need to modify it so that there’s much less risk of airborne transmission. We need to look at building something like the Howard Springs facility in every state and territory of Australia.
"If we didn’t have the hotel quarantine system, there’s no question that Australia would have a terrible epidemic, just like Europe or America"Dr Zoë Hyde
Should future quarantine facilities be located in rural and remote areas or in outer Perth with access to hospital facilities?
We need to keep our quarantine facilities in major cities for logistics reasons.
Even once the bulk of the population is vaccinated against COVID, will Australia still continue to need to use quarantine facilities for those returning from overseas travel?
We’ll need to keep the quarantine system in place until all Australians – including children and adolescents – have had the opportunity to be vaccinated. That means having two doses of the vaccine for full protection. It’s possible that we’ll also need to give everyone a third booster dose to make sure they’re fully protected from the variants. We will be able to open up to international travel again, but the process will have to be a careful and gradual one.
Do you believe we need to pause allowing returned travellers to enter Australia from countries struggling to cope with the pandemic’s third wave and new highly transmissible variants?
I think it’s a good idea to restrict arrivals from countries that have very high levels of community transmission or have dangerous variants. Every arrival is a risk, and so we need to do what we can to keep the risk as low as possible. This is particularly important while we don’t have many people vaccinated in Australia, because we’re still very vulnerable. There are things we could do to reduce the risk, like requiring people to be vaccinated before they come. That won’t eliminate the risk, because some vaccinated people can still transmit the virus, and that could easily spark an epidemic here. But having people vaccinated before they come to Australia will reduce the risk.