Hypochlorous acid solution is a potent antiviral agent against SARS‐CoV‐2.

Aim: A novel coronavirus, termed severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) suddenly appeared in Wuhan, China, and has caused pandemic. In this study, we evaluated antiviral activity of purified hypochlorous acid (HClO) against coronaviruses such as SARS‐CoV‐2 and transmissible gastroenteritis virus (TGEV) responsible for pig diseases. Materials and Results: In a suspension test, 28.1 ppm HClO solution inactivated SARS‐CoV‐2 in phosphate‐buffered saline with the reduction of 104 of 50% tissue culture infectious dose per ml (TCID50 per ml) within 10 s. When its concentration increased to 59.4 ppm, the virus titre decreased to below the detection limit (reduction of 5 logs TCID50) within 10 s even in the presence of 0.1% foetal bovine serum. In a carrier test, incubation with 125 ppm HClO solution for 10 min or 250 ppm for 5 min inactivated SARS‐CoV‐2 by more than 4 logs TCID50 per ml or below the detection limit. Because the titre of TGEV was 10‐fold higher, TGEV was used for SARS‐CoV‐2 in a suspension test. As expected, 56.3 ppm HClO solution inactivated TGEV by 6 logs TCID50 within 30 s. Conclusions: In a carrier test, 125 ppm HClO solution for 10 min incubation is adequate to inactivate 4 logs TCID50 per ml of SARS‐CoV‐2 or more while in a suspension test 56.3 ppm HClO is adequate to inactivate 5 logs TCID50 per ml of SARS‐CoV‐2 when incubated for only 10 s regardless of presence or absence of organic matter. Significance and Impact of the Study: Effectiveness of HClO solution against SARS‐CoV‐2 was demonstrated by both suspension and carrier tests. HClO solution inactivated SARS‐CoV‐2 by 5 logs TCID50 within 10 s. HClO solution has several advantages such as none toxicity, none irritation to skin and none flammable. Thus, HClO solution can be used as a disinfectant for SARS‐CoV‐2. [ABSTRACT FROM AUTHOR]