Weather played a limited role in early spread of Covid-19, research finds

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The paper concluded that human behaviour and government interventions played a far larger role in the spread of the virus at the onset of the pandemic’s first wave. - Luke MacGregor/Bloomberg
The paper concluded that human behaviour and government interventions played a far larger role in the spread of the virus at the onset of the pandemic’s first wave. - Luke MacGregor/Bloomberg

Weather had little impact on the spread of the coronavirus in the early days of the pandemic, according to new research published in Nature Communications.

The paper - which analysed Covid-19 transmission in 409 places in the 20 days after the virus first arrived - concluded that human behaviour and government interventions played a far larger role in the spread of the virus at the onset of the pandemic’s first wave.

“At the beginning of the pandemic, there was lots of speculation about the impact of meteorological conditions on the spread of the coronavirus… and assumptions this would be similar to other seasonal respiratory viruses,” said Dr Rachel Lowe, an associate professor at the London School of Hygiene and Tropical Medicine and co-author of the report.

“But analysing the transmission in these 409 cities in 26 countries across the globe with very different weather conditions suggests this was not the case,” she told the Telegraph. “And so I think at the moment, Covid policy really shouldn’t be based on meteorological conditions.”

The paper assessed the impact of different factors on the spread of Covid-19 by estimating the impact on the effective reproduction number (R) - a measure of the average number of people an infected individual passes the virus onto at a specific point in time.

While the R number dropped by 0.087 for every 10 degree jump in the temperature, early interventions (such as social distancing or travel restrictions, not lockdowns) were associated with a decrease of 0.285 - roughly six times greater.

The researchers wrote: “We found no weather conditions in which transmission is impeded if precautions (social distancing, mask use, etc.) are not taken. These results support the statement that, to date, Covid-19 interventions are critical regardless of meteorological conditions.”

The paper focused on the very early stages of the pandemic, when human susceptibility was high because the global population had no prior immunity to the coronavirus.

Dr Lowe said it was possible that, as the virus shifts to become endemic, it becomes more seasonal, but she warned against complacency. While this study focused on the early days of the pandemic, countries with warmer climates - including India and Brazil - have since been hit by brutal waves of Covid-19.

“Transmission is very much about human susceptibility and human behaviour, which is often driven by interventions rather than the weather conditions themselves,” Dr Lowe said. “Policymakers shouldn’t say, ‘oh we’re heading into summer and therefore it’ll be better’, because actually that could lead to complacency.

“Instead the take home message it: there are much bigger factors driving transmission than the meteorological conditions alone.”

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