Coronavirus: Sunlight, heat and humidity destroys Covid-19, says US agency

Washington, United States - Ultraviolet rays have been found to have a potent impact on the coronavirus.

The new coronavirus is quickly destroyed by sunlight, according to a new study announced by a senior US official on Thursday, offering hope that its spread may ease over the summer.
William Bryan, science and technology advisor to the secretary of the Department of Homeland Security, told reporters at the White House that government scientists had found ultraviolet rays had a potent impact.
"Our most striking observation to date is the powerful effect that solar light appears to have on killing the virus, both surfaces and in the air," he said.
"We've seen a similar effect with both temperature and humidity as well, where increasing the temperature and humidity or both is generally less favorable to the virus."
He then showed a slide summarising the results of the experiment that were carried out at National Biodefense Analysis and Countermeasures Center.
It showed that the virus's half life -- the time taken for it to reduce to half its amount -- was 18 hours when the temperature was 70 to 75 degrees Fahrenheit (21 to 24 degrees Celsius) with 20 per cent humidity on a non-porous surface.
This includes surfaces like door handles and stainless steel.
But the half-life dropped to six hours when humidity rose to 80 per cent -- and just two minutes when sunlight was added to the equation.
When the virus was aerosolised -- meaning suspended in the air -- the half-life was one hour when the temperature was 70 to 75 degrees with 20 per cent humidity.
In the presence of sunlight, this dropped to just one and a half minutes.
Bryan concluded that summer-like conditions "will create an environment with a transmission can be decreased."
But he cautioned that reduced spread did not mean the pathogen would be eliminated entirely and social-distancing guidelines cannot be fully lifted.
"It would be irresponsible for us to say that we feel that the summer is just going to totally kill the virus and then if it's a free-for-all and that people ignore those guides," he said.
The findings could bolster hopes that the coronavirus will mimic the behaviour of other respiratory diseases like influenza, which typically are less contagious in warm weather.
But the coronavirus has also proven lethal in warm-weather places like Singapore, raising broader questions about the impact of environmental factors.
President Donald Trump said the findings should be interpreted cautiously, but also claimed vindication for previously suggesting that the coronavirus might recede in summer.
"I once mentioned that maybe it does go away with heat and light. And people didn't like that statement that much," he said at his daily briefing on Thursday.