In Vitro Virucidal Effects of Ultraviolet Light Prototypes on RNA viruses

Ultraviolet-C (UVC) has been used to cause virus inactivation. The virucidal activity of three UV light lamps [UVC high frequencies (HF), UVC+B LED and UVC+A LED] was evaluated against the enveloped feline coronavirus (FCoVII), a surrogate model of SARS-CoV-2, the enveloped vesicular stomatitis virus (VSV), and the naked encephalomyocarditis virus (EMCV). Virucidal assays were performed at different time points of UV-light exposure (i.e., 5, 30 minutes and 1, 6, and 8 hours), placing each virus 180 cm below the perpendicular irradiation of the lamp and 1 and 2 meters from the perpendicular axis. We found that the UVC HF lamp had virucidal effects (≥96.8% of virus inactivation) against FCoVII, VSV and EMCV after 5 minutes of irradiation at each distance analyzed. Moreover, the UVC+B LED lamp had the highest inhibitory effects on FCoVII and VSV infectivity (≥99% of virus inactivation) when these viruses were settled below the perpendicular axis of the lamp for 5 minutes. Conversely, the UVC+A LED lamp was the least effective, achieving ≥85.9% inactivation of enveloped RNA viruses after 8 hours of UV exposure. Overall, UV light lamps, and in particular UVC HF and UVC+B LED ones, had a rapid and strong virucidal activity against distinct RNA viruses, including coronaviruses.