Evaluation of the efficacy of chlorous acid water and sodium hypochlorite solution against SARS-CoV-2 in the presence of organic matter

Abstract

Chlorous acid water and sodium hypochlorite solution are effective disinfectants against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the virus that caused the pandemic. Recent studies have shown that both compounds have equivalent inactivation effects when tested on purified viruses. However, in practical applications, the presence of organic matter is common and can significantly affect disinfectant performance. We conducted several experiments comparing these two disinfectants under different conditions to better understand their practical efficacy. When an infected cell culture medium (serum-free) was used as the test virus, chlorous acid water and sodium hypochlorite solution showed reduced efficacy. This decrease was attributed to the presence of aa in the medium. Notably, sodium hypochlorite solution showed a more pronounced reduction in potency compared with chlorous acid water. In addition, we evaluated the SARS-CoV-2 inactivation effects of chlorous acid water and sodium hypochlorite solution under various organic loading conditions simulating real-world contamination scenarios such as blood, vomit and saliva. The organic materials used included BSA, SRBCs, polypeptone, FBS and artificial saliva. The results showed that chlorous acid water demonstrated superior resilience to organic matter interference compared with sodium hypochlorite solution. These results suggest that chlorous acid water may be more effective than sodium hypochlorite solution in inactivating viruses on contaminated surfaces, particularly in healthcare settings where organic contamination is common. In summary, our research suggests that chlorous acid water may be a more effective disinfectant in practical settings.

Keywords: COVID-19; free available chlorine (FAC); oxychlorine-based disinfectants; virucidal agents; virus inactivation capability.

Fig. 1.. Inactivation of SARS-CoV-2 by chlorous acid water and sodium hypochlorite solution in the presence of organic matter. SARS-CoV-2 was incubated with oxychlorine disinfectants in the presence of 0.03% BSA (b), [0.3% SRBCs+0.3% BSA] (c), 0.5% PP (d), 5% FBS (e), artificial saliva (f) or no organic matter (containing 1/10-diluted DMEM) (a) for 10 min, and infectivity was measured by the TCID₅₀ method. Data points are shown as red circles (chlorous acid) and blue triangles (sodium hypochlorite solution). Measured values were fitted to an approximate equation based on the Chick–Watson model. Approximation equations and R² values are shown in the graphs. R², coefficient of determination; Log₁₀(N/N₀), log reduction in survival ratio. The 95% CIs for the fitted curves were calculated using JMP and are coloured in red (chlorous acid) and blue (sodium hypochlorite solution).