US scientists: Sunlight and humidity kill coronavirus the fastest

Sunlight and humidity kill coronavirus the fastest
US government scientists found UV rays had a potent impact on the pathogen. Source: Reuters
3 Min Read

Daily US Times: Coronavirus dies the fastest when it is exposed to direct sunlight, US scientists claimed, though a study cited has not yet been made public and awaits external evaluation.

Science and technology adviser to the Department of Homeland Security, William Bryan, said that government scientists found ultraviolet rays had a potential impact on the pathogen. He offers hope that the spread of coronavirus may ease over the summer.

“The virus dies quickest in the presence of direct sunlight,” Bryan said on Thursday’s press conference.

He added: “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.”

“We’ve seen a similar effect with both temperature and humidity as well, where increasing the temperature and humidity or both is generally less favourable to the virus.”

Ultraviolet light has long been known has a sterilising effect, because the radiation damages the virus’s genetic material and its ability to replicate.

But coronavirus has also proven lethal in warm-weather places such as Thailand, Malaysia, and Singapore, raising broader questions about the impact of environmental factors.

“The evidence is not supporting [the sunlight] theory”, said Dr Margaret Harris from the World Health Organization.

Harris said: “I’m sorry but we cannot hope that summer is going to have the effect that many people hope it will.”

It would be “irresponsible” to say the warmer summer months will eliminate coronavirus, Bryan warned but said that time period would provide an “opportunity to get ahead” of the pandemic.

The research mentioned by Bryan has not yet been released for review, making it difficult for independent experts to comment on how robust its methodology was.

Past studies have not found reliable evidence that higher humidity of spring and summer or warmer temperatures will help tamp down the spread of the virus.

18 hours versus 6 hours

Bryan shared a slide summarising the major findings of an experiment carried out at the Countermeasures Center in Maryland and the National Biodefense Analysis.

He said, on nonporous surfaces such as stainless steel, the new coronavirus takes 18 hours to lose half its strength in a dark, low-humidity environment.

In a high humidity environment, that half-life dropped to six hours, and when the virus was exposed to high sunlight and humidity, the half-life dropped to two minutes, he said.

Researchers found a similar effect with the coronavirus that was suspended in the air – simulating the sneezing or coughing that often spreads the disease. In a dark room, the virus maintained half its strength for an hour.

You may read: Nearly all patients on ventilators in a health system died, study finds