Disinfection of SARS-CoV-2 using UVC reveals wavelength sensitivity contributes towards rapid virucidal activity

SARS-CoV-2 can be disinfected using ultraviolet-C (UVC) light. For effective inactivation strategies, design and implementation, knowledge of UVC wavelength sensitivity, and disinfection rate of the relevant pathogen are required. This study aimed to determine the inactivation profile of SARS-CoV-2 using UVC irradiation with different wavelengths. Specifically, the study determined dosage, inactivation levels, and wavelength sensitivity of SARS-CoV-2. Assessment of SARS-CoV-2 (isolate USA/WA1-2020) inactivation at peak wavelengths of 259, 268, 270, 275 and 280 nm was performed using a plaque assay method. A UVC dose of 3.1 mJ/cm ² using 259 and 268 nm arrays yielded log reduction values (LRV) of 2.32 and 2.44, respectively. With a dose of 5 mJ/cm ² , arrays of peak wavelengths at 259 and 268 nm obtained similar inactivation levels (LRV 2.97 and 2.80 respectively). The arrays of longer wavelength (270, 275 and 280 nm), demonstrated lower performances (≤LRV 2.0) when applying an irradiation dose of 5 mJ/cm ² . Additional study with the 268 nm array revealed that a dose of 6.25 mJ/cm ² is enough to obtain a LRV of 3. These results suggest that 259 and 268 nm are the most efficient wavelengths for SARS-CoV-2 inactivation compared to longer UVC wavelengths, allowing the calculation of disinfection systems efficacy.