Comparison of Virucidal Activity between Weakly Acidified Chlorous Acid Water and Sodium Hypochorite Solution

The virucidal activities of weakly acidified chlorous acid water (WACAW) was characterized in comparison to those of sodium hypochlorite solution (NaClO), using polioviruses type 1 and 3. In the absence of interfering substances, more than 10-4-reduction of the infectivity was achieved by NaClO at 5 ppm and by WACAW at 0.75 ppm of free available chlorine concentration. Similarly, in the presence of 0.5% polypepton, more than 4 logs (99.99% or more) reduction of infectious virus for PV-1 and PV-3 was achieved by the incubation with NaClO at 2,000 ppm but not at 500 ppm, while it was achieved by the incubation with WACAW at 100 ppm but not at 50 ppm. These results show that WACAW was more effective than NaClO at the same free available chlorine concentrations regardless of the presence of interfering substances, suggesting a general advantage of the WACAW for practical applications as a disinfectant.