Lessons learned from other coronaviruses that have emerged during the 21st century (SARS-CoV and MERS-CoV) show a slightly different scenario. A study that tracked weather conditions during the SARS outbreak in China in 2003 showed that the peak in infections occurred in spring weather conditions. (It was not possible to confirm this phenomenon by other studies since the virus died out later).
Regular outbreaks of MERS also occur in spring (March to May) in the Middle East. However, this may have less to do with climate than with camel biology. Humans can transmit the MERS virus to each other or become infected through contact with camels. Young camels are a source of infection and new animals are born during the month of March. However, the precise role these animals play in transmitting the virus and the exact mode of transmission are not known.
You can also see what happened in the southern hemisphere during the winter there. South Africa has reported more than 700,000 cases and had a significant peak in July, while New Zealand controlled the infection very well and recorded fewer than 2,000 cases of COVID-19 in the same period.
These two countries are very different in many ways, so it is not very useful to compare them directly. But it looks like the colder weather in July and August was probably not the main factor in the trajectory of infection rates. New Zealand appears to have succeeded in containing the spread of SARS-CoV-2 thanks to geography, the quality of its health system and the effectiveness of the public health response. She could have done it, whatever the weather.
Early data from Australia suggests low humidity would be a factor to watch out for and a better indicator of the risk of an increase in COVID-19 than temperature. However, in Melbourne, a major epidemic erupted in July, coinciding with a cold snap. This led to strict containment which continued until October.
Overall, it would not be surprising to see a higher number of COVID-19 cases during the colder months. But the only thing we know for sure about SARS-CoV-2 is that new viruses can surprise us.
We also know that coming into close contact with other people gives the virus an opportunity to spread, regardless of the temperature. People who do not live under the same roof must therefore maintain a physical distance and wear a face covering in confined spaces.
Unfortunately, it is only by going through this pandemic that we will learn exactly how climatic variations are affecting the situation.
This text first appeared on The Franco-Canadian site of The Conversation. Reproduced with permission.
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