Scientists from around the world have been investigating and delving into SARS-CoV-2 for more than a year, a new coronavirus that has caused the pandemic from which it seems we are beginning to recover thanks to the range of vaccines available around the globe. Although there is still much to do. We face new challenges that involve all kinds of investigations that can provide us with clues to live in the presence of this mysterious murderer.
Many concepts of how to avoid or keep COVID-19 away from us (social distancing, washing hands with soap or hydroalcoholic gel, wearing the mask properly …) supported by science remain unchanged to this day.
Other notions, such as droplet contact as the primary mode of transmission, were modified when emerging evidence showed that, under certain conditions, the virus could remain airborne for prolonged periods.
Now, a major study developed by UC Santa Barbara, Oregon State University, the University of Manchester and ETH Zurich, has found, following previous research published in July 2020, that simulated sunlight “rapidly inactivated the SARS-CoV-2 ”on surfaces, which laboratory experiments show inactivation of sunlight several times faster than theory predicts. In fact, during laboratory experiments, viruses were inactivated more than eight times faster than they theoretically should have been.
“The theory assumes that inactivation works by causing UV-B rays to hit the RNA of the virus and damage it,” says UC Santa Bárbara professor of mechanical engineering and lead author, Paolo Luzzatto-Fegiz, in the study that collects the Journal of Infectious Diseases. However, judging by the discrepancies between the experimental results and the predictions of the theoretical model, the research team considered that the inactivation of RNA by UV-B “might not be the whole story.”
The experiments demonstrated virus inactivation times of about 10 to 20 minutes, much faster than theory predicts.
“The theory predicts that inactivation should occur an order of magnitude slower,” explains Luzzatto-Fegiz. In the experiments, viruses in simulated saliva and exposed to UV-B lamps inactivated more than eight times faster than theory would have predicted, while those that were cultured in full growth medium prior to exposure to the UV-B rays were inactivated more than three times faster than expected. For the mathematics of the theory to fit the data, according to the work, SARS-CoV-2 would have to exceed the highest UV-B sensitivity of any currently known virus .
To explain this gap, they argue that we need to look beyond ultraviolet B (UVB) and start paying more attention to ultraviolet A (UVA), the lower-energy component of sunlight associated with skin aging. And it is that UV-A radiation could be interacting with some reactive intermediate molecules that, in turn, could be interacting with the virus, accelerating its inactivation.
Anyway, at the moment they are just guesswork. “Scientists do not yet know what is going on. Our analysis points to the need for additional experiments to separately test the effects of specific wavelengths of light and medium composition,” concludes Luzzatto-Fegiz.
If so, it would be a promising solution, as UVA rays are safe and easy to generate with LED bulbs that are many times more powerful than natural sunlight. They could be used as a disinfection method to slow the spread of COVID-19 in high-risk spaces such as public transportation and hospitals.
Referencia: “UVB Radiation Alone May Not Explain Sunlight Inactivation of SARS-CoV-2” by Paolo Luzzatto-Fegiz, Fernando Temprano-Coleto, François J Peaudecerf, Julien R Landel, Yangying Zhu and Julie A McMurry, 5 February 2021, The Journal of Infectious Diseases.
DOI: 10.1093/infdis/jiab070
