NICASTRO, FABRIZIOFABRIZIONICASTROSIRONI, GIORGIAGIORGIASIRONIAntonello, EEAntonelloBIANCO, ANDREAANDREABIANCOBiasin, MMBiasinBrucato, JRJRBrucatoERMOLLI, IlariaIlariaERMOLLIPARESCHI, GiovanniGiovanniPARESCHISalvati, MMSalvatiTOZZI, PaoloPaoloTOZZITrabattoni, DDTrabattoniClerici, MMClerici2021-09-272021-09-2720212045-2322http://hdl.handle.net/20.500.12386/31059Solar UV-C photons do not reach Earth’s surface, but are known to be endowed with germicidal properties that are also effective on viruses. The effect of softer UV-B and UV-A photons, which copiously reach the Earth’s surface, on viruses are instead little studied, particularly on single-stranded RNA viruses. Here we combine our measurements of the action spectrum of Covid-19 in response to UV light, Solar irradiation measurements on Earth during the SARS-CoV-2 pandemics, worldwide recorded Covid-19 mortality data and our “Solar-Pump” diffusive model of epidemics to show that (a) UV-B/A photons have a powerful virucidal effect on the single-stranded RNA virus Covid-19 and that (b) the Solar radiation that reaches temperate regions of the Earth at noon during summers, is sufficient to inactivate 63% of virions in open-space concentrations (1.5 × 103 TCID50/mL, higher than typical aerosol) in less than 2 min. We conclude that the characteristic seasonality imprint displayed world-wide by the SARS-Cov-2 mortality time-series throughout the diffusion of the outbreak (with temperate regions showing clear seasonal trends and equatorial regions suffering, on average, a systematically lower mortality), might have been efficiently set by the different intensity of UV-B/A Solar radiation hitting different Earth’s locations at different times of the year. Our results suggest that Solar UV-B/A play an important role in planning strategies of confinement of the epidemics, which should be worked out and set up during spring/summer months and fully implemented during low-solar-irradiation periods.ELETTRONICOenArticle10.1038/s41598-021-94417-92-s2.0-85110935764WOS:000692201400022https://www.nature.com/articles/s41598-021-94417-9FIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering