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

Abstract

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 titer of SARS-CoV-2 after UV irradiation (0.1 mW/cm 2) at 222 nm for 10-300 seconds 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 seconds) resulted in 88.5 and 99.7% reduction of viable SARS-CoV-2 based on the TCID 50 assay, respectively. In contrast, the copy number of SARS-CoV-2 RNA did not change after UVC irradiation even after a 5-minute irradiation. Conclusions: 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.

Quantitative Evaluation of SARS-CoV-2 Inactivation Using a Deep Ultraviolet Light-Emitting Diode

“…In the current global pandemic of SARS-CoV-2, means to inactivate viruses and prevent infections must be taken. DUV irradiation is one powerful and effective way to combat various microorganisms including SARS-CoV-2 and related coronaviruses [10][11][12][13][14][15][16][17]. However, in order to establish commonly and widely usable inactivation apparatuses/techniques using DUV, reliable quanti ed data that can serve as a solid standard for their development are required; the length of the DUV irradiation periods, which wavelength, and what doses of DUV are needed for SARS-CoV-2 inactivation.…”

“…While the biological effects of DUV light have been widely proven across different types of viruses [14,[16][17][18][27][28][29][30][31], the precise mechanism by which the DUV light inactivates viruses remains to be elucidated [18]. Several studies reported that virus inactivation by DUV irradiation is primarily caused by the photochemical reactions of nucleic acids [18,32,33].…”

“…Thermal treatment is also known to be effective for SARS-CoV-2 inactivation [8,9]. Photochemical inactivation, especially using deep ultraviolet (DUV) light (λ < 300 nm), is the most time-saving and e cient way to inactivate SARS-CoV-2 and related coronaviruses [10][11][12][13][14][15][16][17]. DUV light irradiation exerts a critical effect on the infectivity of microorganisms and viruses probably by damaging their RNAs [18].…”

Effect of intermittent irradiation and fluence-response of 222 nm ultraviolet light on SARS-CoV-2 contamination

“…However, recent reports have shown the effectiveness of ultraviolet light (UV) irradiation for inactivating SARS-CoV-2 [ [4] , [5] , [6] ]. The effectiveness of 222 nm UVC light for disinfecting surfaces contaminated with SARS-CoV-2 has been reported [ 7 ]. In this previous study, the 222 nm UVC-emitting device, Care222™(Ushio Inc., Tokyo, Japan; Dimensions: 205 mm x 150 mm x 50 mm) was used and the effect of 0.1 mW/cm 2 222 nm UVC with multiple irradiation times on surfaces contaminated with SARS-CoV-2 was investigated [ 7 ].…”

“…The effectiveness of 222 nm UVC light for disinfecting surfaces contaminated with SARS-CoV-2 has been reported [ 7 ]. In this previous study, the 222 nm UVC-emitting device, Care222™(Ushio Inc., Tokyo, Japan; Dimensions: 205 mm x 150 mm x 50 mm) was used and the effect of 0.1 mW/cm 2 222 nm UVC with multiple irradiation times on surfaces contaminated with SARS-CoV-2 was investigated [ 7 ]. When Care222™ was installed on the ceiling or wall, the UV irradiance of distant areas such as desks and floors was lower than that of a previous study setting [ 7 ].…”