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Kaoru OBINATA　Pandemics of microorganism are serious problem such as corona virus induced disease 2019(COVID-19), and the infectious diseases rapidly transmitted via airborne or aerosol among community space. To prevent aerosol infections, ozone and chlorine dioxide gases are practical methods in room air. However, ozone requires relatively high concentrations for this purpose, which might be toxic to humans present in the room. On the other hand, the low concentration of chlorine dioxide gas and aqueous solution are sufficiently effective against aerosol infection for the causative microorganism, and it is expected that when it is used in combination with a high-efficiency particulate air filter, it will be highly safe with high prevention effect and cost effectiveness.Juntendo Medical Journal2022. 68(5), 465-472Special ReviewsNew Countermeasures Against Infections with/after COVID-19:IntroductionScience the current global outbreak of severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2) infection, the development of effective and safe methods to inactivate viruses in a manned environment have been required1). Respiratory viruses mainly transmitted human-to-human via droplets or aerosols. To control infec-tions, not only standard precaution but also counter-measures at the spatial environment are important, and the establishment of economically healthy and effective infection prevention methods is desired. Disinfection methodsOzoneOzone gas is a strong oxidant2) and has long been used to inactivate pathogenic microbes in water3, 4). It can be used to inactivate microbes on the surfaces Key words: chlorine dioxide, COVID-19, aerosol infection, disinfectionDepartment of Prevention Medicine for Mass Infection, Juntendo University Graduate School of Medicine, Tokyo, JapanCorresponding author: Kaoru ObinataDepartment of Prevention Medicine for Mass Infection, Juntendo University Graduate School of Medicine2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, JapanTEL: +81-3-5802-1075　FAX: +81-3-5800-0216　E-mail: kobinata@juntendo.ac.jp355th Triannual Meeting of the Juntendo Medical Society “Farewell Lectures of Retiring Professors” 〔Held on Mar. 30, 2022〕〔Received　Jul. 11, 2022〕〔Accepted　Aug. 17, 2022〕J-STAGE Advance published date: Oct. 15, 2022Copyright © 2022 The Juntendo Medical Society. This is an open access article distributed under the terms of Creative Commons Attribution License (CC BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original source is properly credited. doi: 10.14789/jmj.JMJ22-0030-Rof objects and aerosols. Hudson et al. found ozone inactivated viruses, including mouse coronavirus, on glass and stainless steel5). They reported that 20-25 ppmv ozone with 90% relative humidity was effective at inactivating 12 viruses on hard or porous surfaces5).However, high concentrations of ozone need for the disinfection of room air or object surfaces, and problem remains its toxicity to humans and animals6). Sokolowska et al. reported a mouse experiment where a single exposure to 1 ppmv ozone for 60 min caused damage to the bronchiolar epithelium within 2 hours, disrupted epithelial tight junctions, and promoted cell death, which was followed by reactive oxygen species production6). This result indicates the difficulty of using ozone as a disinfec-tant against viruses in the presence of humans in rooms. Chronic exposure of humans to ozone causes the progressive and irreversible loss of alveolar 465Is Chlorine Dioxide a Useful and Safe Disinfectant?