Will winter impact the severity of COVID outbreaks?

Anastasia Tsirtsakis

31/05/2021 4:11:10 PM

In Australia and other parts of the world, a drop in temperatures has often been met with an increase in cases. But according to a virologist, human behaviour has a lot to answer for.

Woman wears a mask and holds an umbrella.
Wearing face masks when social distancing is not an option is among the recommendations made by UK researchers to help avoid transmission of COVID-19.

As Victorians endure yet another period of heightened COVID restrictions, memories of last winter’s 112-day lockdown have started to resurface.
Over the course of the pandemic, experts’ understanding of the novel virus and how it spreads has evolved, with evidence indicating there may be a seasonal effect, consistent with other respiratory viruses.
Further to that, laboratory experiments have found SARS-CoV-2 thrives out of direct sunlight in cold, dry conditions and that artificial ultraviolet radiation can inactivate viral particles on surfaces, as well as in aerosols.
So should Australians brace themselves for a new wave heading into winter? Perhaps.
But according to University of Queensland virologist Associate Professor Ian Mackay, more so than the weather, it is the changes in human behaviour from season to season that may explain any uptick in spread.
‘There is evidence that viruses are affected by humidity [and] by temperature … But how big an effect is what we don’t tend to discuss and what is, probably, impossible to measure really,’ he told newsGP.
‘The evidence we have for SARS-CoV-2 transmission involves aerosols. So when people are fairly close together for a period of time, or they’re congregated in a room for a longer period of time, transmission happens.
‘So it’s what we do in response to something – whether it’s a change in temperature or whether it’s the school holidays. When schools in, things are different from when school’s out.
‘Those sorts of things do need to be included in any graph that talks about seasonality because seasonality isn’t just about temperature and weather, it’s about human behaviour.’
Associate Professor Mackay cites the UK as an example where there may be more opportunity for spread. Given the cooler climate, it often results in people gathering indoors with poor ventilation.
‘Where there’s poor airflow, where you can’t open a window because it’s freezing outside, where you don’t have any kind of filtration or air scrubbers in place, then yes, you will see more cases result from a gathering of people where there are some proportion of people that might be positive,’ he said.
Recognising the role of poor ventilation, UK researchers recently released a report summarising ways to reduce transmission by wearing face masks and social distancing, and hand and surface cleaning.
However, they say good ventilation with adequate outdoor air supply is particularly important in crowded indoor spaces.
This is similar for cases of colds and flus, which are known to spike in winter months. But Associate Professor Mackay says seasonality has more of an effect for endemic viruses that most, if not all, Australians have at least partial immunity to.
‘With a new virus that we have no immunity to … that virus will spread simply wherever it can because opportunities abound,’ he said.
‘Later, when we’re all vaccinated, it will be harder for it to spread and things that we’ll see happen are going to be more like what we see with those other viruses – they’ll be influenced by temperature, humidity, amount of time and UV.’
At the time of publication (31 May 2021), more than 4.2 million doses of coronavirus vaccines had been administered to Australians, with momentum increasing since the vaccination program was opened to those aged 40–49.
But while vaccines are a big part of Australia’s pandemic exist strategy, even when the country reaches a level of herd immunity, Associate Professor Mackay says personal hygiene measures, such as handwashing and mask wearing, will still be key to curbing transmission.
‘Apart from lockdown scenarios, we’ve seen quite a big effect from hand washing, from staying apart from people, from not travelling as much on public transport,’ he said.
‘Mask use is something we should adopt going forward forever. It should be advertised as a good thing by our health authorities.
‘We’re focused on this current pandemic, but we could knock down our numbers of flu. Flu kills every year; it kills in the old age, and it has a massive impact on the very, very young – they’ve got the highest hospitalisation rates of any group when it comes to flu.
‘When I was in Vietnam, just recently, they had stalls in their markets just dedicated to selling masks and I laughed at them because I’ve learned this issue about masks too late myself. But I understand now that masks represent a way that we can slow transmission.
‘It’s all about human behaviours.’
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Dr Nirmala Boyapati   1/06/2021 7:32:23 AM

Side effects due to clots with AstraZeneca has been the factor in vaccine hesitancy. If we were able to offer Pfizer to all the uptake will increase instantly.

Dr Mark David De Kretser   3/06/2021 4:15:53 AM

Over 12 months into the pandemic I am still stunned by how little virologists and epidemiologists understand about the seasonality of respiratory viruses. Infection is an interaction between a virus and and a HOST, yet host factors are consistently ignored.
Good science begins with observation and it is obvious that these specialists never speak with the doctors who actually work on the front line and see seasonality in action. I live in the UK and I can tell you that people in the UK spend a lot of time inside with others in poorly ventilated rooms in Summer too! Next you will be telling us that Covid toes aren't caused by Covid as the dermatologists tried to.