SARS-CoV-2 Virus Dies in Seconds Under UV-C

New research finds that seconds of exposure to 254nm ultraviolet light inactivates the coronavirus that causes COVID-19.

It would be nice to finish this depressing pandemic year with some good news. Perhaps this can do the trick. Experiments at the National Emerging Infectious Diseases Laboratories of Boston University have demonstrated “Rapid and complete inactivation of SARS-CoV-2 by ultraviolet-C irradiation.” The paper was published in Scientific Reports , one of Nature‘s open-access journals, on 30 Dec 2020 by a team of 9 researchers led by Nadia Storm and Lindsay McKay.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has devastated global public health systems and economies, with over 52 million people infected, millions of jobs and businesses lost, and more than 1 million deaths recorded to date. Contact with surfaces contaminated with droplets generated by infected persons through exhaling, talking, coughing and sneezing is a major driver of SARS-CoV-2 transmission, with the virus being able to survive on surfaces for extended periods of time. To interrupt these chains of transmission, there is an urgent need for devices that can be deployed to inactivate the virus on both recently and existing contaminated surfaces. Here, we describe the inactivation of SARS-CoV-2 in both wet and dry format using radiation generated by a commercially available Signify ultraviolet (UV)-C light source at 254 nm. We show that for contaminated surfaces, only seconds of exposure is required for complete inactivation, allowing for easy implementation in decontamination workflows.

The researchers specify the particular wavelength of ultraviolet light required out of 3 common ranges of UV:

There are three types of UV, including UV-A (315–400 nm), UV-B (280–315 nm) and UV-C (100–280 nm), of which UV-C is most commonly employed in germicidal applications. At a wavelength of 254 nm, viral inactivation can be attributed to direct UV-C light absorption and photochemical damage to nucleic acid, leading to the disruption of viral replication.

Earlier research had shown that UV-C was effective in killing the coronavirus, but uncertainties remained about what particular wavelength was most effective for which environments (surfaces, air, droplets etc.) and how long an exposure was needed. The US Food and Drug Administration (FDA) reported what was known on August 19. Healthline also published a list of “facts and myths” about UV light around the same time. It agreed that UV-C is promising, but concluded that the standard actions of hand-washing, masks and social distancing were best because “the optimal length of exposure, wavelength, and dose of UVC light needed for killing the new coronavirus is yet to be determined.”

Now, Boston University appears to have the answer. For killing the virus on wet and dry surfaces, UV-C at 254 nm for mere seconds is enough. The Signify device that can do this is also commercially available. (It should be noted that 4 of the 9 authors work for Signify, and the Signify Research company sponsored the study.) In the experimental tests, viruses were inactivated completely in just 4 to 5 seconds, both for samples containing dried virus samples and samples with the virus in wet droplets. In 6 seconds. 99% of the virus was deactivated.

Some Caveats

UV-C at this wavelength and intensity can cause eye damage, so it “should only be used with proper training or where people are not at risk of being exposed.” The research team is next experimenting with far-UV wavelengths (207-222 nm) that should be safer. The tests were run under controlled conditions. The paper did not specify which commercially-available UV-C product by Signify is appropriate for practical use. More experiments should also be run to see how well the treatment performs under those expected in real-world situations.

Positive Alternatives

Many hospitals already use powerful UV radiation blasts to disinfect hospital rooms between patients. If a hand-held device could be used in these institutions within seconds, many businesses could conceivably re-open. For example, restaurants could disinfect tables and chairs between customers, and airlines could disinfect the interiors of planes. Those most at risk, such as the elderly in nursing homes, could be kept safer if walls, beds, and eating utensils could be disinfected regularly. Perhaps circulating air in vents could be irradiated with UV-C as well. There could even be products for home use, if experiments demonstrate that UV at safer wavelengths prove effective.

Although several techniques exist for inactivating SARS-CoV-2, the lack of proven effective tools and interventions have allowed for the unmanageable spread of the virus in the human population. Our results show that UV-C is a powerful tool that can be applied extensively in a wide range of public institutions including hospitals, nursing homes, workplaces, schools, airports and shopping centers to disinfect contaminated equipment and surfaces to prevent and reduce SARS-CoV-2 contact transmission.

FDA approved vaccines are making the rounds, with more coming. Millions have already been vaccinated, and other therapies continue to be tested and approved. But since prevention is better than cure, methods for disinfecting homes and businesses ahead of exposure could add to the arsenal of weapons for combating COVID-19 which turned 2020 into a nightmare for people around the world. If the nanobody technologies (Aug-Sept 2020) advance rapidly too, there is increasing hope that 2021 will see the end of the pandemic sooner than the dire predictions still being made, worrying citizens who otherwise face 3 to 6 more months of lockdowns. If PPEs and ventilators could be rolled out within weeks, why not UV-C devices?

Update 1/7/2021: A Canadian company has also demonstrated that its UV-C device can kill the coronavirus within 8 seconds at one foot, and 30 seconds at two feet (Medical Xpress).

You may wish to share the paper in Science Advances with politicians, businesses and friends. Instead of simply complaining to mayors and governors about how unfair their lockdown policies are, it’s better to have reliable scientific evidence of alternatives that work. Aim to create a win-win situation.