Chlorine dioxide is a more potent antiviral agent against SARS-CoV-2 than sodium hypochlorite

Background A new coronavirus (SARS-CoV-2) abruptly emerged in Wuhan, China, in 2019 and rapidly spread globally to cause the COVID-19 pandemic. Aim To examine the anti-SARS-CoV-2 activity of the potent disinfectant Cleverin, the major disinfecting component of which is chlorine dioxide (ClO 2 ); and to compare the results with that of sodium hypochlorite in the presence or absence of 0.5% or 1.0% foetal bovine serum (FBS). Methods Concentrated SARS-CoV-2 viruses were treated with various concentrations of ClO 2 and sodium hypochlorite and 50% tissue culture infective dose was calcurated to evaluate the antiviral activity of each chemical. Findings When SARS-CoV-2 viruses were treated with 0.8 ppm ClO 2 or sodium hypochlorite, viral titre was decreased only by 1 log 10 TCID 50 /mL in 3 min. However, the viral titre was decreased by more than 4 log 10 TCID 50 /mL when treated with 80 ppm of each chemical for 10 s regardless of presence or absence of FBS. It should be emphasized that treatment with 24 ppm of ClO 2 inactivated more than 99.99% SARS-CoV-2 within 10 s or 99.99% SARS-CoV-2 in 1 min in the presence of 0.5% or 1.0% FBS, respectively. By contrast, 24 ppm of sodium hypochlorite inactivated only 99% or 90% SARS-CoV-2 in 3 min under similar conditions. Notably, except for ClO 2 , the other components of Cleverin such as sodium chlorite, decaglycerol monolaurate, and silicone showed no significant antiviral activity. Conclusion Altogether, the results strongly suggest that although ClO 2 and sodium hypochlorite are strong antiviral agents in absence of organic matter but in presence of organic matter, ClO 2 is a more potent antiviral agent against SARS-CoV-2 than sodium hypochlorite.