Aerodynamic Characteristics and RNA Concentration of SARS-CoV-2 Aerosol in Wuhan Hospitals during COVID-19 Outbreak

Yuan Liu; Zhi Ning; Yu Chen; Ming Guo; Yingle Liu; Nirmal Kumar Gali; Li Sun; Yusen Duan; Jing Cai; Dane Westerdahl; Xinjin Liu; Kin-fai Ho; Haidong Kan; Qingyan Fu; Ke Lan

MSAs in general have higher concentration of SARS-CoV-2 aerosol with biomodal size distributions compared to PAA in both hospitals during the first batch of sampling in the peak of COVID-19 outbreak. For Renmin Hospital sampling sites, the air circulation in MSA by design is isolated from that of the patient rooms. While for Fangcang Hospital, the nonventilated temporary PARR has limited air penetration from the patient hall where the SARS-CoV-2 aerosol concentration was generally low. We believe one direct source of the high SARS-CoV-2 aerosol concentration may be the resuspension of virus-laden aerosol from the surface of medical staff protective apparel while they are being removed. These resuspended virus-laden aerosol originally may come from the direct deposition of respiratory droplets or virus-laden aerosol onto the protective apparel while medical staff having long working hours inside PAA, as shown from the SARS-CoV-2 deposition results in ICU room. Another possible source is the resuspension of floor dust aerosol containing virus that were transferred from PAA to MSA. The two virus-laden aerosol sources also appear to correspond to the sub-and supermicron peaks found in size-segregated samples. We hypothesize the submicron aerosol may come from the resuspension of virus-laden aerosol from staff apparel due to its higher mobility while the supermicron virus-laden aerosol may come from the resuspension of dust particles from the floors or other hard surfaces. The findings suggest virus-laden aerosols could first deposit on the surface of medical staff protective apparel and the floors in patient areas and are then resuspended by the movements of medical staff. The second batch of TSP samples taken in Fangcang MSAs all tested negative with reduced number of patients from > 200 to 100 per zone and implementation of more rigorous and thorough sanitization measures in Fangcang. The comparison of the two batches of samples showed the effectiveness and importance of sanitization in reducing the airborne SARS-CoV-2 in high risk areas.