Will the arrival of sunny days in the northern hemisphere have an impact on the coronavirus epidemic? This is one of the big unknowns since the start of this crisis, and the White House believes it has provided an initial response. According to a study by the United States government, presented Thursday April 23 in Washington, the virus responsible for the Covid-19 pandemic weakens in a hot and humid atmosphere as well as in the sun’s rays.
“Our most striking observation to date is the powerful effect that sunlight seems to have to kill the virus, both on surfaces and in the air”said senior Homeland Security official Bill Bryan.
“We have seen a similar effect on both temperature and humidity. Rising temperatures or humidity, or both, are generally less favorable for the virus. “
Caution at the White House
US Vice President Mike Pence described the sightings as“Encouraging”. Donald Trump, for his part, remained cautious but noted that the United States could be in a better position with the arrival of summer.
“If the heat is good, if the sunlight is good, I think it’s a very good thing. “
“We have identified some of the weak links in the virus’s transmission chain. We have identified that heat and humidity are weak elements in this chain. We identified that sunlight, UV rays were a weakness in this chain ”said Bill Bryan, a science and technology expert with the Department of Homeland Security.
This study may fuel hopes that the coronavirus will mimic the behavior of other respiratory illnesses, such as the flu, which are generally less contagious in the summer. But the coronavirus has also been shown to be deadly in places like Singapore when temperatures were summer there, casting doubt on a link between virus behavior and environmental factors.
Life span between eighteen hours and two minutes
In support of his claims, the expert presented some figures from this study conducted at the National Biodefense Analysis and Countermeasures Center. According to these data, a half-life of the virus, namely the time necessary to halve its power, is eighteen hours with a temperature between 21 and 24 degrees Celsius, with 20% humidity on a surface not – porous. This includes surfaces such as door handles.
But this half-life is reduced to six hours when the humidity rises to 80%, and only to two minutes when sunlight is added to the equation. When the virus is suspended in the air, the half-life is one hour with a temperature of 21 to 24 degrees Celsius and 20% humidity. With the same humidity, the same temperature, but with the addition of sunlight, this time drops to a minute and a half.
Bill Bryan concluded that summer conditions could create “An environment in which transmission can be reduced”. But that does not mean that the pathogen is completely eliminated. And the results of this one study cannot justify lifting social distancing measures currently in effect in the United States, he warned.
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