Disinfectant effectiveness against SARS-CoV-2 and influenza viruses present on human skin: model-based evaluation

Hirose, Ryohei; Bandou, Risa; Ikegaya, Hiroshi; Watanabe, Naoto; Yoshida, Takuma; Daidoji, Tomo; Naito, Yuji; Itoh, Yoshito; Nakaya, Takaaki

OBJECTIVES: Disinfection effectiveness against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on human skin remains unclear due to the hazards of viral exposure. An evaluation model, which has been previously generated using human skin obtained from forensic autopsy samples, accurately mimics in vivo skin conditions for evaluating the effectiveness of disinfection against the virus. Using this model, we evaluated the disinfection effectiveness against viruses on human skin. METHODS: Ethanol (EA), isopropanol (IPA), chlorhexidine gluconate (CHG), and benzalkonium chloride (BAC) were used as target disinfectants. First, disinfectant effectiveness against SARS-CoV-2 and influenza A virus (IAV) was evaluated in vitro. Disinfectant effectiveness against SARS-CoV-2 and IAV on human skin was then evaluated by titrating viruses present on the skin after applying each disinfectant on the skin for 5-60 s. RESULTS: Both, SARS-CoV-2 and IAV on human skin were completely inactivated within 5 s by 40-80% EA and 70% IPA (log reduction values [LRVs] were >4). However, SARS-CoV-2 and IAV were barely inactivated by 20% EA (LRVs were <1). In vitro evaluation showed that compared to EA and IPA, CHG and BAC were significantly inferior in terms of disinfection effectiveness. Conversely, the disinfection effectiveness of CHG and BAC against SARS-CoV-2 was higher on human skin than in vitro, and increased with increases in their concentration and reaction time (LRVs of 0.2% CHG/0.05% BAC were >2, and LRVs of 1.0% CHG/0.2% BAC were >2.5). CONCLUSIONS: Proper hand hygiene practices using alcohol-based disinfectants such as EA/IPA effectively inactivate SARS-CoV-2 and IAV on human skin.