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Will coronavirus get worse as winter sets in?

By Kate Doyle, Wednesday March 25, 2020 - 08:28 EDT
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Rugging up is not going to stop you getting COVID-19. - ABC

The jury is still out on how much the weather is or is not influencing COVID-19, but a bad flu season on top of the current health crisis is the last thing we need this winter.

Rumours about coronavirus and the weather have been spreading, mostly through people in the Northern Hemisphere hoping their coming summer will help stop the spread.

That speculation, however, is less welcome for those of us where winter is on the way.

As with most things about this epidemic, it is complicated and there is lots we still don't know.

There is reason to think COVID-19 may spread more quickly in winter; it is a respiratory illness and spreads in a similar way to a cold or a flu.

There is definitely a flu season in winter in temperate regions, the parts of the world with defined seasons (like southern Australia).

There is a variety of reasons the weather conditions themselves could encourage flu to spread:
found influenza virus transmissions were more favourable in cooler, less-humid conditions;
Warm temperatures can also kill the flu virus, but only at temperatures — so above temperatures commonly induced by the weather.

Linda Selvey from the school of public health at the University of Queensland said it might be that the influenza virus lived longer in cooler, less-humid weather.

"But it may also be related to such things as in winter time, people tend to stay indoors more and may have inflamed noses and mouths simply from being out in the cold," she said.

There's a but coming ...

Those scenarios are well and good for temperate regions, but they fall apart somewhat when you look at the tropics.

Tropical regions, where there aren't distinctive temperature-driven seasons, still experience just as much flu but it comes all year round, Dr Selvey said.

Plus, what happens with flu (strains of influenza virus) will not necessarily be the same with COVID-19 (or the SARS-COV-2 virus).

"If influenza might be more stable in cooler, low-humidity environments, it's possible that COVID-19 is also more stable in those circumstances," she said.

"The thing is we really don't have enough information to know for sure."

A paper out of China doing the rounds on social media suggests the spread of COVID-19 had been slower as the temperature and humidity increased.

"[But] while there may be a relationship between temperature, humidity and COVID-19, I don't think that that paper can show that categorically," Dr Selvey said.

"I think there are a number of flaws in that paper."

She said it had compared countries without taking into account their different responses to the virus, when some countries had taken action that would have limited the number of cases.

Sherry Towers, an expert in computational epidemiology at Arizona State University, agreed, pointing out that the paper had not been peer reviewed.

The lack of testing resources in many countries, and changes in test supplies, meant most "confirmed case" data was likely not reflective of the real number of infections at the time, she said.

"This virus is so transmissible (even more transmissible than 1918 pandemic flu), it will likely not go away in summer, even if transmission does in fact get damped somewhat by temperature," Dr Towers said.

The authors of the paper in question are yet to respond to a request for an interview.

is a good example of coronavirus still spreading even through hot, humid weather.

COVID-19 will likely get worse regardless

"It's quite possible that the rate of spread could increase, regardless of the temperature, because the biggest factor relates to human behaviour," Dr Selvey said.

"If people who are infectious are having contact with a lot of other people, then that will be the major driving force for the spread of COVID-19 anywhere in the world, regardless of temperature and humidity."

Kirsty Short, a research fellow at UQ's school of chemistry and molecular biosciences, said it was not as clear cut as you get cold, therefore you get sick.

"If you're hypothermic, then obviously a lot of your body's systems shut down and that could impair immunity," she said.

"Catching a cold is not that you get cold, it's that you get infected with a specific virus."

Putting on an extra jumper is not going to stop you getting coronavirus.

When flu collides with COVID-19

"My particular concern with the winter season is not the temperature per se, but the fact that it means coronavirus will be co-circulating with our regular flu season," Dr Short said.

During a bad flu season, the healthcare system can be under a lot of strain; if a bad flu year combines with the coronavirus outbreak, she said it could really tip the system over.

"That's why this year, more than ever, we're encouraging people to flu vaccinate.

"Not because it specifically protects them against coronavirus, but because it helps reduce that burden on the healthcare system."


© ABC 2020

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