Abstract
Past experiments demonstrated SARS-CoV-2 inactivation by simulated sunlight; models have considered exclusively mechanisms involving UVB acting directly on RNA. However, UVA inactivation has been demonstrated for other enveloped RNA viruses, through indirect mechanisms involving the suspension medium. We propose a model combining UVB and UVA inactivation for SARS-CoV-2, which improves predictions by accounting for effects associated with the medium. UVA sensitivities deduced for SARS-CoV-2 are consistent with data for SARS-CoV-1 under UVA only. This analysis calls for experiments to separately assess effects of UVA and UVB in different media, and for including UVA in inactivation models.
Lay summary Recent experiments have demonstrated that SARS-CoV-2 is inactivated by simulated sunlight; however, there are still many unknowns, including the mechanism of action and which part of the light spectrum is principally responsible. Our analysis indicates the need for targeted experiments that can separately assess the effects of UVA and UVB on SARS-CoV-2, and that sunlight inactivation models may need to be expanded to also include the effect of UVA. A first UVA-inclusive model is also proposed here. These findings have implications for how to improve the safety of the built environment, and for the seasonality of COVID-19.
Competing Interest Statement
J McMurry is a co-founder of Pryzm Health, a bioinformatics company focused on rare disease phenomics (unrelated to this manuscript).
Footnotes
Summary This study shows that the prevailing assumption that sunlight inactivation of SARS-CoV-2 is driven exclusively by UVB is inconsistent with available data and with UVB-based theory. The alternative model proposed herein suggests that UVA could play a significant role, likely through an indirect mechanism dependent on the medium.