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Health authorities clarify position on COVID aerosol spread

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Recognition of the potential for airborne spread of the coronavirus has been taken one step further by the Infection Control Expert Group (ICEG).
 
Recently issued Communicable Diseases Network Australia (CDNA) National Guidelines now state that there is ‘a gradient from large droplets to very small particles (aerosols), which may contribute to transmission of SARS-CoV-2 in certain situations’.
 
‘These include during aerosol generating procedures in clinical settings … Certain behaviours, such as singing and shouting, could also increase the force and range of spread of both large and small particles,’ the guidance states.
 
‘In poorly ventilated, crowded indoor environments, small particles, which are normally rapidly dispersed may remain suspended or be recirculated for longer periods.’
 
However, the latest recommendations by the ICEG on the use of personal protective equipment (PPE) still only state that healthcare workers ‘may consider’ use of a particulate filter respirator (PFR), such as a P2 or N95, instead of a surgical mask in ‘specified settings’. These are limited to emergency departments, residential care facilities, COVID-19 wards, and other hospital in-patient settings, in areas with significant community transmission, where one or both of the following apply: 

• For the clinical care of patients/residents with suspected or confirmed COVID-19, who have cognitive impairment, are unable to cooperate, or exhibit challenging behaviours (ie shouting, by patients/residents who are agitated or find instructions hard to follow)
• Where there are high numbers of suspected or confirmed COVID-19 patients/residents AND a risk of challenging behaviours and/or unplanned aerosol-generating procedures (eg including intermittent use of high flow oxygen)

Deputy Chief Medical Officer Dr Nick Coatsworth also recently came under fire on Twitter after suggesting health authorities had recognised aerosol transmission since July, with a number of people calling on the ICEG to update its guidance for healthcare workers to reflect the threat posed by aerosols.
 
However, ICEG member, infectious disease specialist and microbiologist Professor Peter Collignon told newsGP he doesn’t believe there are any discrepancies, but rather a slight difference in interpretation.
 
‘It’s based on risk assessment. The guidelines essentially say if there’s a reasonable chance that there might be aerosols there, and not just because you’re nebulizing, [take extra precaution],’ he said.
 
Associate Professor Jane Munro, member of the Victorian Healthcare Infection Prevention and Wellbeing Taskforce, told newsGP the ICEG’s recognition of aerosol transmission is a step in the right direction, but pointed out it is not always possible to assess aerosol risk accurately.
 
‘Those guidelines are a definite improvement in acknowledging aerosol spread. This is an evolving science and we’ve just got to make sure we keep moving with what the science says,’ she said.

‘GPs have generally gone above and beyond this and have taken precautionary principles in their practices, looking after their own health and wellbeing of their staff and themselves.
 
‘But realistically, how are you predicting when a patient is going to suddenly scream or shout or cough when you’re doing something? How are you suddenly going to pick who the patient that gets distressed or otherwise is?’


It is not always possible to assess aerosol risk accurately. 
Asymptomatic presentations for COVID-19 may also make risk assessment difficult. But Professor Collignon argues the risk is relatively low.
 
‘Ninety per cent of COVID transmission is by people with symptoms, asymptomatic might be 20%. But they don’t cough, don’t sneeze and so they’re much less able to transmit it,’ he said.
 
‘And again, all the epidemiological studies show that.’
 
When it comes to the available evidence, Professor Collignon says the important question is whether there is actually a difference between effectiveness of surgical and N95 masks in curbing transmission.
 
The ICEG states that ‘current evidence does not indicate any additional benefit from the use of a PFR rather than a surgical mask, in preventing SARS-CoV-2 transmission during routine care of patients/residents with suspected or confirmed COVID-19’.
 
While Professor Collignon says there is ‘no doubt aerosols are factor’, he doesn’t believe they are to a significant degree.
 
‘For the general spread of COVID, they do not seem to be a big factor because even in households, generally, if somebody’s got it and you’re with them for 14 days, it’s variable, but around 15% of people get it, more so if you’re sleeping in the same bedroom, etcetera,’ he said.
 
‘If aerosols were a big factor, you’d expect the infection rates … to be closer to 80% or 90%, not down where it is. Hospitals are not that different to all the other environments where people have it.
 
‘[Also], if aerosols were a major feature in the spread of COVID, we would have no hope of controlling it because it would mean an ordinary surgical mask and cloth mask don’t work. It means you’d have to keep all restaurants, bars, clubs closed … [and] you’d have to close all staff rooms in hospitals, etcetera.’
 
The view is contrary to an article published in Science that claims there is ‘overwhelming evidence’ that inhalation of SARS-CoV-2 ‘represents a major transmission route’ for COVID-19.
 
‘Individuals with COVID-19, many of whom have no symptoms, release thousands of virus-laden aerosols and far fewer droplets when breathing and talking,’ the authors state.
 
‘Thus, one is far more likely to inhale aerosols than be sprayed by a droplet, and so the balance of attention must be shifted to protecting against airborne transmission.’
 
But Professor Collignon says he suspects it is rather the role of droplets that has been misunderstood.
 
‘The trouble with our view on droplets is in certain conditions droplets go further than one or two metres,’ he said.
 
‘They can actually, in my view, go much further, particularly if you’re downwind … from a fan or an air conditioner. Equally when people shout or sing, it goes further than two metres … that’s where we’ve been caught out.’
 
What is needed, he says, is better governance and training in infection control.
 
‘The major issue here is that we need better ventilated rooms, we need not crowded rooms, we need to be careful with people,’ he said.
 
‘If you look at most of the infections at northern Tasmania, it came from patients, but then it went from person to person in staff rooms [and] handover rooms, because people were in there in too crowded conditions. The same happened in Melbourne again.
 
‘So the problem I have with this aerosol theory is everybody thinks “[if] I wear an N95 mask, end of problem”. The majority of spread is because people don’t follow proper things that have been set already.
 
‘In other words, keep your distance, four square metre rule, and if you can’t do the four square metre rule, you don’t use the room, which means you can’t do a lot of things we currently do.’
 
Associate Professor Munro agrees that healthcare workers, including GPs need to be thinking about the precautionary principle and assessing their workspaces.
 
‘Please do not get complacent. We are not there yet and you really, really must keep getting pandemic fit,’ she said.

‘How is your workplace? What is your team doing? Have you got your behaviours sorted, healthcare worker to healthcare worker?
 
‘Don’t get slack about it because we need to make sure we keep those systems in place and yes, a lot of these other things are really important in terms of the safety and the protection of healthcare workers –including things like PPE and fit testing – but a lot of the other stuff is really important too.

‘Making sure that we do have a safe place to be able to eat and got to the toilet at work, and that we have all of those other bigger safety things in place around ventilation to make sure that we’re right for other waves that come to wherever in Australia we work – and that we get things like age care sorted. That’s really important.’

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aerosols airborne transmission COVID-19 PPE

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