SARS-CoV-2, the coronavirus that causes COVID-19, is quickly destroyed by sunlight. That’s according to the findings of U.S. scientists, although the revelations are still awaiting confirmation.
William Bryan, science and technology adviser to the secretary of the Department of Homeland Security, told reporters gathered at the White House that government scientists have made an important discovery about SARS-CoV-2. According to the latest findings, ultraviolet rays have a strong effect on the pathogen, raising hopes that the increase in cases will decline during the summer months.
– Our most striking observation is the strong effect that sunlight appears to have on the virus. It kills it both on the surface and in the air. We have seen a similar effect with both temperature and humidity,” said William Bryan.
The research paper has not yet been published, making it difficult for independent scientists to comment. It has long been known that ultraviolet light has a sterilizing effect because it destroys a virus’s genetic material and its ability to replicate. The key question was what intensity and wavelength of UV light was necessary to kill the virus. The researchers were unsure whether radiation of this wavelength occurs naturally in the summer.
– It would be good to know how these studies were done and how the results were measured. I don’t think they were done poorly, but it is known that there are several different ways to count the survival of the virus, said Benjamin Neuman, a biologist at the University of Texas who was not involved in the study.
Bryan said the study was conducted by the National Biodefense Analysis and Countermeasures Center in Maryland. According to his data, the virus’ half-life (the time it takes to reduce the virus to half its amount) is 18 hours at 21-24 o C with 20 percent humidity. This is true on non-porous surfaces, such as door handles or stainless steel. But the half-life dropped to six percent when the humidity rose to 80 percent. When sunlight was added to the mix, the virus survived for just two minutes.
When the virus was atomized, or suspended in the air, the half-life was one hour in the same temperature and humidity range. In the presence of sunlight, the half-life of the virus in air was reduced to only 1.5 minutes. It is obvious to conclude that the summer months provide an environment that limits the spread of the pathogen.