Comparison of virucidal activity between weakly acidified chlorous acid water and sodium hypochlorite solution

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