Warmer weather won’t have big impact on slowing COVID-19: experts

By | April 10, 2020

TORONTO — As Canadians hunker down for yet another weekend at home, many have begun holding onto hope that warmer weather will prevent the spread of COVID-19, much like seasonal influenza, spurring rumours that summer will bring respite from strict physical distancing measures.

Preliminary research has suggested that warmer temperatures may help to slow the spread of the novel coronavirus, but experts warn that pandemics don’t behave in the same way as seasonal outbreaks.

In other words: summer weather won’t stop COVID-19, nor will it mean an end to physical distancing.

“It looks, so far, that warmer weather might do a little bit. But it won’t have a huge impact as far as we can tell, and we certainly can’t rely on that to reduce the cases,” Chris Bauch, a mathematics professor at the University of Waterloo who has done extensive research into the spread of SARS and the 2009 pandemic influenza, told CTVNews.ca by phone Thursday.

“The biggest impact is continuing our physical distancing efforts.”

THE EVIDENCE

Early analysis by scientists at MIT found that most coronavirus transmissions have occurred in regions with low temperatures, between 3 and 17 degrees Celsius, noting that countries with equatorial climates and those currently experiencing summer account for fewer than six per cent of global cases so far.

While the peer-reviewed study suggests that temperatures may play a role in the virus’s effectiveness, it does not stop it the transmission altogether.

At least two other studies have examined the link between weather and the spread of COVID-19, including one that found Chinese cities with higher temperatures and more humid environments reported a slower rate of infection early in the outbreak.

The studies have been examined by members of the U.S. National Academy of Sciences committee who concluded this week that they do not offer enough evidence to suggest that the onset of summer will prevent the spread of coronavirus in the U.S.

This comes after U.S. President Donald Trump has suggested several times that the virus will “die” with the warmer weather.

CTVNews.ca spoke with three experts who all agreed that warmer weather will only play a small role in decreasing the spread of the virus.

But Ken Denike, a geography professor at the University of British Columbia who has been researching geographic and seasonal factors associated with SARS and COVID-19, notes that there is some evidence that our physiological response to warmer climates may play a role too.

“The health authorities in China take great store by measuring the erythrocyte sedimentation rate (ESR), which they use to sort of tell how healthy a patient is,” he told CTVNews.ca by phone.

“It’s been noted that the ESR drops in the summer and that makes it very difficult for the virus to sort of grab on in terms of getting into the blood.

My read on it is that, yes, in the summer, the influenza rate and COVID-19 rate will drop, but doesn’t mean it’ll be completely gone. This is especially for healthy people… for people are not healthy it doesn’t seem to be a solution.”

Denike notes that it would be “criminal or close to it” to suggest that summertime could solve the pandemic.

WHY ARE SOME VIRUSES SEASONAL?

Experts note that seasonal impact on the influenza virus is well established and a similar slowdown has been seen in the spread of the SARS outbreak, also caused by a coronavirus.

But Bauch notes that pandemics don’t behave the same way as seasonal outbreaks — and we still have lots to learn about this virus in particular.

“Season influenza happens more or less the same time every year. And there are known seasonal factors that cause that,” he explained.

“Vitamin D is a part of certain antimicrobial peptide that our body uses to fight influenza — we get a lot of vitamin D in the summer, for example.”

He notes that different diseases can be seasonal for different reasons.

“Sometimes it’s related to how susceptible the host is. Sometimes it’s flooded through seasonality and our contact patterns,” Bauch explained.

“For example, for some infections spread with kids being crowded together in school in September. There’s a correlation with the school calendar for measles, but we don’t see that for other infections.”

Pandemic influenza, he notes, exhibits different behaviours.

“Pandemic influenza can come at any time of the year. We’ve had pandemic waves in the spring and the fall in the pattern in past pandemics… and of course, coronavirus is not influenza and so many of the same things will not apply,” he said.

Bauch says Canadians can expect to heed physical distancing advice until July, noting that halting the spread of the virus is largely dependent on the healthcare system, the availability of a vaccine, and our co-operation.

Edited by CTVNews.ca editor Michael Stittle

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