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WHO acknowledges COVID-19 airborne transmission may be possible


Matt Woodley


8/07/2020 4:21:47 PM

Despite only recently pushing back against such claims, scientists from the global health body have now said there is emerging – but not definitive – evidence.

Dr Maria Van Kerkhove
WHO technical lead for COVID-19 Dr Maria Van Kerkhove said microscopic respiratory droplets are a possible route for infection. (Image: AAP)

The World Health Organization’s (WHO) acknowledgement came after more than 230 scientists called on health authorities to address ‘every potentially important’ transmission pathway in order to slow the spread of COVID-19.
 
Many epidemiologists have been hesitant to label coronavirus as ‘airborne’, as there is no evidence it is able to spread in a similar manner to highly infectious diseases such as measles, which can linger in the air for hours and is estimated to be up to six times more contagious.
 
Nonetheless, the WHO’s technical lead for COVID-19 Dr Maria Van Kerkhove told reporters that microscopic respiratory droplets are a possible route for infection.
 
‘We have been talking about the possibility of airborne transmission and aerosol transmission as one of the modes of transmission of COVID-19,’ Dr Van Kerkhove said, before adding that the WHO is still collecting evidence and will soon publish a scientific brief on the virus’ modes of transmission.
 
ANU infectious diseases physician and microbiologist Professor Peter Collignon believes there is the potential for airborne spread in specific settings, but told newsGP he does not want the risk to be overstated.
 
‘You can come up with a laboratory experiments that show these aerosols stay in the air … but the epidemiological data, the follow-up data, show that this mainly spreads when you’re close to people for long periods of time, particularly indoors when there’s [poor] ventilation,’ he said.
 
‘If aerosols were a big feature with this, [if there were infected] people in the same household, you’d expect to have 70%, 80%, 90% infection rates, but instead it’s closer to 10% or 20% of the house.
 
‘[This] is good news because if it really was spread a lot with aerosols … we’d all either have to be in spacesuits or not breathe for the next three years.’
 
However, UNSW respiratory physician and epidemiologist Professor Guy Marks, who contributed to the open letter, told newsGP its contents are simply focused on lowering the risk of coronavirus spreading in general.
 
‘Recognising the role of smaller particles, transmitted by the airborne route, focuses attention on ventilation, air exchange rates and the indoor environment,’ he said.
 
‘It remains unclear how important [safeguards like masks] are. Where there is widespread community transmission, it does seem a wise addition to other measures, mainly to protect others from the wearer.’ 
 
The WHO’s technical lead for infection prevention and control Dr Benedetta Allegranzi acknowledged there is ‘emerging evidence’ of airborne transmission, but that it is not definitive.
 
According to Dr Allegranzi, part of the ongoing review of evidence will be aimed at understanding the importance of transmission by aerosols compared with larger droplets, as well as the dose of the virus needed for infection from aerosols.
 
‘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,’ she said.
 
‘We have to be open to this evidence and understand its implications regarding the modes of transmission and also regarding the precautions that need to be taken.’
 
Professor Collignon, who is also a member of Australia’s Infection Control Expert Group, has ‘no trouble’ with people calling for adequate ventilation as ‘all the data’ show that being outdoors is much safer than indoors.
 
But he said Australia’s success at reducing the coronavirus’ R number to less than one using already established infection control procedures shows there is currently a limited need for other enhanced protections, such as P2 or N95 masks.
 
‘What [predominantly airborne transmission] would mean is that everybody’s got to be wearing N95 masks all the time and doing it properly. Well, the probability of that’s low,’ he said.
 
‘My view is, let’s … do what we can in a practical way that really decreases transmission. I fully accept it may not decrease it to zero. But what this is about is getting the effective R number below one and at low numbers and keeping it there.
 
‘The bottom line is this virus is not going to go away. So whatever we do, we’re going to have to do for the next two or three years.’
 
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Dr Ian Mark Light   9/07/2020 9:54:31 AM

This means that in the return to schooling classrooms and staff rooms have to improve their ventilation by opening windows the health benefit outweighs the energy demand .
A report from Japan using “supercomputer modelling” suggested opening windows in operating commuter trains with physical distancing would reduce Covid 19 spread.
Medical Centres then have to look at their ventilation in waiting rooms consulting rooms and treatment rooms .
Many clinics have consulting rooms with no windows .
In the future medical clinics ought be built with fresh air ventilation and viral filtering incorporated into the design.
But it also means outdoor activities with physical distancing can be allowed and artists could conduct outdoor concerts with people physically distanced and with masks and these concerts could be beamed to a wider audience .
Live theatre and art galleries could be outdoors under tents but with fresh air flowing .


Dr Atoosa Salimi   9/07/2020 1:07:45 PM

Australia is definitely at the start of this pandemic saga. Although, factors such as the geography and lower population density has helped Australia in achieving a lower R0 at the start, as long as international flights are still open, Australians will be spending longer and longer times in the lock down.
The ONLY way approaching this pandemic is to STOP international passenger flights immediately and to encourage wearing masks in our society.
Judging by what is currently happening in Melbourne and Sydney, one can only say that we are only as strong as our weakest link in this pandemic.


Dr Ragupathy Renganathan   9/07/2020 1:37:02 PM

As we are aware many of the Respiratory viruses are Aerosol spread.
The contact and proximity of closeness(either indoor or outdoor) is the most important factor in spreading.
The second factor for the contagion will be for the duration of survival of the virus in the air.Hope soon the longevity of Covid 19 out in the air will be very valuable in 'social distancing'.


Dr Ian Mark Light   9/07/2020 6:42:31 PM

The WHO spokesperson acknowledged that good ventilation in indoor spaces is important .
Opening Windows to allow fresh air in is mentioned as the simplest option .
This can be achieved at schools in the older trams in some medical clinics and hospitals and some offices
Another alternative is virally filtered Airconditioning systems .
Hospitals have negative pressure rooms that keep virus particles out of the room and there are triage tents with specialised filtration .
What was emphasised is that in the outdoors Viral spread is far less so more outdoor activities are possible .
The Arts industry then in the future could have outdoor plays concerts and galleries with limited people physically distanced and beamed to a wider audience .
Aged Care Homes can set up temporary structures outside allowing for relatives to visit and doctors to attend for examinations and councelling .


Dr Janice Faye Sheringham   10/07/2020 12:05:19 AM

So division and conjecture remain! Given the agreed R number of the virus(2.5), on first principles it is highly UNLIKELY that aerosol transmission is a SIGNIFICANT contributor to disease transmission! If the R number was the same order of magnitude as, say, measles or varicella, BOTH of which are well recognised as having aerosol transmission, THEN we would indeed be facing a very serious situation! While I agree that masks have a role to play in limiting AEROSOL spread, it cannot be a coincidence that those much more densely populated countries - Japan and Taiwan, neither of whom closed businesses nor locked down huge swathes of their populations during this pandemic, employed widespread testing, contact tracing and quarantine of infected people, ALSO encouraged/required their populations TO WEAR MASKS IN PUBLIC! Their results speak to the efficiency of their systems, the support FROM their people for the measures used AND their widespread compliance BECAUSE THEY UNDERSTOOD!