Ventilation measures to control aerosol transmission based on COVID-19 outbreaks in hospitals in Japan

COVID-19 outbreaks occurred in several hospitals, and the National Institute of Infectious Diseases, local authorities, and universities carried out investigations into ventilation in hospitals. The results indicated that ventilation performance was insufficient to prevent aerosol infection due to poor air conditioning, equipment maintenance, and existing ventilation design guidelines. The authors investigated guidelines for ventilation measures for general patient wards with the cooperation of The Society of Air-Conditioning and Sanitary Engineers of Japan and the Japanese Society for Infection Prevention and Control. Based on a survey of COVID-19 outbreaks in hospitals, ventilation countermeasure plans for 3 stages (a. normal conditions, b. increased risk of outbreaks, and c. infected patients treated) were compiled.