Australian states and territories may have a handle on controlling the spread of COVID-19 so far, but the impending arrival of winter is a major cause for concern in coronavirus management, say some of Australia’s leading disease experts.
All the work we’ve done towards keeping coronavirus under control during the warmer autumn months may quickly come undone as we head into winter, they say.
“We don’t know what effect winter will have,” said Australia’s Chief Health Officer, Professor Brendan Murphy.
“We don’t know exactly how this virus will behave in temperature and climate. That’s one of the things we are concerned about in Australia.”
Experts told The Guardian Australia that cooler temperatures may affect the behaviour and spread of a virus in three interconnected ways.
Some viruses that can survive for longer in a more limited temperature range may develop a more robust ‘envelope’, so simply washing hands with soap and water may not be as effective as it is in warmer months.
Also, when temperatures drop, human behaviour changes, so staying indoors more often may actually work against us and make the virus easier to spread.
Finally, the circulation of influenza, colds, allergies and other viruses will lower the population’s immunity levels.
Seasonality can cause an increase in the spread of viruses, says Alfred Hospital respiratory physician and Monash University Associate Professor Tom Kotsimbos.
“That is well established, but whether we understand that deeply is another thing,” he said. “It does have an influence, but we don’t understand it specifically. This is a new virus, and that does not mean it will be like the others.
“We know it’s about the biology of the virus, the general and specific immunity of us and the environmental and behavioural conditions.
“It’s interesting that [COVID-19] has spread all over the world quite quickly – both north and south,” he said, suggesting the new virus’s efficacy was not really dependent on temperature and but more on the lowering population immunity during colder months.
Australian National University infectious disease physician and microbiologist Professor Peter Collignon agrees that it’s more likely COVID-19 will spread more in winter.
“Winter is coming up and it will probably be more likely to be transmitted,” he said.
“Basically every virus that we have and know about is transmitted more often in winter, during cold times. But equally, they can transmit during warmer months. Look at Singapore, for instance, which is never in winter.
“We’ve had transitions of COVID-19 when it was our autumn.
“But that happens with influenza, it transmits in summer and autumn, but we have fewer cases.
“The major outbreaks have been in the United States, Europe and China and they were in winter. But equally, Korea had an outbreak in February, which they got under control, even though it was winter.”
Research from Hong Kong University shows that it spreads more quickly and lives longer in colder temperatures.
Australian National University infectious disease epidemiologist Dr Meru Sheel says transmission is aided by increased time spent indoors.
“We see an increase in respiratory diseases in general because people tend to spend more time in confined spaces, and we tend to keep the windows closed,” said Dr Sheel.
“There’s less ventilation, and also there are more people in that space. In summer, we spend more time outside; in winter, you spend more time inside.
“I think the most important thing is public health hygiene, like washing your hands, using a tissue to blow your nose.
“As we go into flu season, people should get vaccinated for flu. If you are at home with symptoms then avoid physical contact with family members, hugs and kisses, and if you have symptoms, go get tested for COVID-19.”
All experts agree that the effect of COVID-19 on top of the flu season will strain our healthcare system and that social distancing – even at home – is more important than ever.
“My concern is that [in winter] people tend to be in closer contact and it coincides with our flu season,” said University of Queensland virologist Dr Kirsty Short.
“My main concern is that when you think of the healthcare system, that does get pushed in a bad flu season. If we combine a moderate flu season with a moderate coronavirus season, that could be problematic.”
“As Australia moves into cooler weather, we are likely to see an increase in respiratory diseases such as common colds, influenza and RSV infections.
“To minimise the pressure on the health system, it will be important for the community to adopt public health prevention measures, get vaccinated, stay at home when unwell and practise social distancing.
“This will also help improve our ability to test for COVID-19 and, in return, protect our vulnerable populations such as the elderly and those with underlying conditions and minimise their risk of exposure to infection with COVID-19. All these factors will contribute towards better control of the outbreak.”
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