Rapid in vitro virucidal activity of slightly acidic hypochlorous acid water toward aerosolized coronavirus in simulated human-dispersed droplets

Abstract

The virucidal activities were evaluated by spraying slightly acidic hypochlorous acid waters (SAHWs) containing various concentrations of free available chlorine - 100, 200, 300 and 500 ppm (SAHW-100, -200, -300 and -500, respectively) - toward aerosol of an avian coronavirus (infectious bronchitis virus: IBV). The viral solution was supplemented with 0.5% fetal bovine serum (FBS) to simulate normal human droplets generated by sneezing or coughing in a real-life scenario. The virus containing 0.5% FBS was sprayed and exposed to SAHWs for a few seconds in a closed chamber, before reaching the air sampler. The results showed that IBV exposed to SAHW-100 and -200 for a few seconds decreased by 0.21 log 10 and 0.80 log 10 , respectively, compared to the pre-exposed samples to SAHWs as controls. On the other hand, reductions of 1.16 log 10 and 1.67 log 10 were achieved following the exposure to SAHW-300 and -500, respectively, within a few seconds. These results suggest that SAHWs have rapid in vitro virucidal activity toward aerosolized IBV. The findings obtained for IBV might basically be applicable in relation to SARS-CoV-2, given the resemblance between the two viruses. To prevent human-to-human transmissions by aerosols, the inactivation of viruses in the air by exposure to SAHWs for a few seconds seems to be an effective way.

The HOCl dry fog–is it safe for human cells?

“…Since the COVID-19 outbreak, many studies have evaluated the germicidal activity of HOCl-based disinfectants at very high concentrations; however, there are limited data examining the cytotoxic effect of HOCl used as a disinfectant [29,[32][33][34][35]. In addition, to achieve maximum germicidal effect on a large area in a shorter time, some researchers have developed dry fogging systems that disperse fine droplets of a disinfectant that penetrate inaccessible areas and cover virtually any surface [29,33,35,36].…”

In vitro cytotoxicity and antibacterial activity of hypochlorous acid antimicrobial agent

“…reported concentration-dependent virucidal activities of HOCl with various concentrations of free available chlorine (100–500 ppm) against aerosolized coronavirus. 48 The weak acid HOCl can dissolve in water to form hypochlorite ion (OCl − ), 21 and the HOCl/OCl − ratio depends on the solution pH. 49 It should be noted that as a disinfectant HOCl is much more effective than OCl − .…”

Evaluation of chlorine dioxide in liquid state and in gaseous state as virucidal agent against avian influenza virus and infectious bronchitis virus

“…Each of the rayon sheet was treated with 2 mL of FBS, microwaved, and then additionally treated with FBS by using a hand spray before the experiment, so as to neutralize the ClO 2 gas on rayon sheets. The aspirator was connected to a bottle filled with a sterilizing agent (mixture of QAC and food additive grade calcium hydroxide) and a suction pump (SP 40, MARKOS-MEFAR, Borezzo, Italy) equipped with high efficiently particulate air filter, similarly to the previous experiment [ 21 ]. The suction pump could collect the air sample at a speed of 35 L/min).…”