Effectiveness of 222-nm ultraviolet light on disinfecting SARS-CoV-2 surface contamination

Kitagawa, Hiroki; Nomura, Toshihito; Nazmul, Tanuza; Keitaro, Omori; Shigemoto, Norifumi; Sakaguchi, Takemasa; Ohge, Hiroki

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has emerged as a serious threat to human health worldwide. Efficient disinfection of surfaces contaminated with SARS-CoV-2 may help prevent its spread. This study aimed to investigate the in vitro efficacy of 222-nm far-ultraviolet light (UVC) on the disinfection of SARS-CoV-2 surface contamination. METHODS: We investigated the number of viable SARS-CoV-2 after UV irradiation (0.1 mW/cm(2)) at 222 nm for 10–300 s using the 50% tissue culture infectious dose (TCID(50)). In addition, we used quantitative reverse transcription polymerase chain reaction to quantify SARS-CoV-2 RNA under the same conditions. RESULTS: One and 3 mJ/cm(2) of 222 nm UVC irradiation (0.1 mW/cm(2) for 10 and 30 s) resulted in 88.5 and 99.7% reduction of viable SARS-CoV-2 based on the TCID50 assay, respectively. In contrast, the copy number of SARS-CoV-2 RNA did not change after UVC irradiation even after a 5-min irradiation. CONCLUSION: This study shows the efficacy of 222-nm UVC irradiation against SARS-CoV-2 contamination in an in vitro experiment. Further evaluation of the safety and efficacy of 222-nm UVC irradiation in reducing the contamination of real-world surfaces and the potential transmission of SARS-CoV-2 is needed.