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COVID-19: No link yet between Warmer Temperatures & Virus Transmission

Many held out hope that the Covid-19 pandemic, like the seasonal flu, would fade away when the weather warmed up. Early speculation, some based on data on other coronaviruses, hinted that the SARS-CoV-2 virus would follow the same patterns. As the number of cases worldwide surpassed 1.5 million, summer seemed like it couldn’t come soon enough.
 
But a new public report, sent to the White House by the National Academies of Sciences, Engineering, and Medicine on Wednesday, puts those fantasies to rest, saying there’s no evidence to support the claim that the pandemic will disappear with warmer weather. That isn’t to say there isn’t any work being done on this topic. 
 
Rather, it’s that the existing studies show conflicting results and are plagued with data and methodology issues, so scientists can’t draw any useful conclusions from them. The National Academies committee who wrote the report based their findings on the scant research available, dividing it in two categories: lab studies and natural history studies.
 
In the former, scientists grow virus particles in a laboratory and stick them on a variety of surfaces at different temperatures and humidities to see how long they survive. Of the four lab studies the committee highlighted, only one is actually published, and the rest are ongoing. The preliminary results are mixed: One study suggests higher temperatures do kill the virus, while other, very early data suggests higher temperatures help the virus live longer.
 
Caveats abound: The relevance of lab results to the real world is very questionable, for one thing, and some labs can’t control for humidity, a very important factor in real life. There’s also the possibility that multiple strains of SARS-CoV-2 may be circulating, each with a potentially different ability to survive the heat.
 
Meanwhile, the six natural history studies — those tracking the virus over time and space — examined in the paper also have conflicting results. They also had their own set of caveats, mostly relating to the quality of the data: One big issue is that the pandemic is occurring mostly in temperate parts of the world (where seasonal changes are mild) during winter months, ruling out scientists’ ability to collect data on the virus’ spread in very cold temperatures.
 
The authors seem open to the possibility that new evidence could show that temperature and Covid-19 spread are related, but the data available now simply doesn’t make that clear. Besides, they note, it’s summer in Australia and Iran, and those countries are experiencing outbreaks, and previous flu pandemics (as opposed to the seasonal flu) didn’t follow any seasonal patterns.
 
Like reports from most health organizations, this one stresses the importance of social distancing — which would be paramount even if new data shows that summer temperatures kill the virus. If you cough or sneeze “close enough to the next susceptible person,” co-author and host microbe scientist David Relman, MD, said, “then temperature and humidity just won’t matter that much.”
 

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