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

The airborne SARS-CoV-2 concentrations in different categorized sites are shown in Table 1 . The ICU, CCU and ward room in PAA of Renmin Hospital had negative test results. Fangcang Hospital workstations in different zones had low concentrations (1-9 copies m -3 ) of SARS-CoV-2 aerosol. The highest concentration in PAA of two hospitals was observed inside the patient mobile toilet room (19 copies m -3 ). In MSAs, the two sampling sites in Renmin Hospital had low concentration of 6 copies m -3 , while the sites in Fangcang Hospital in general had higher concentrations. Particularly, the Protective Apparel Removal Rooms (PARRs) in three different zones inside Fangcang Hospital are among the upper range of airborne SARS-CoV-2 concentration from 18 to 42 copies m -3 in the first batch of sampling. During the second batch of sampling, the two TSP samples in the PARRs had negative test results with reduced number of medical staff and more rigorous sanitization processes in Fangcang. In PUA, SARS-CoV-2 aerosol concentrations were below 3 copies m -3 , except for two occasions: one crowd gathering site near the entrance of a department store with frequent customer flow and one outdoor site next to Renmin Hospital with outpatients and passengers passing by. The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/2020.03.08.982637 doi: bioRxiv preprint Hospital. The peak concentration of SARS-CoV-2 aerosols appears in two distinct size ranges, one in the submicron region with aerodynamic diameter dominant between 0.25 to 1.0 µm, and the other peak in supermicron region with diameter larger than 2.5 µm. The submicron region was dominantly noted in PARRs in Zone B and C of Fangcang Hospital (Figure 1a and 1b) with peak concentration of 40 and 9 copies m -3 in 0.25 to 0.5 µm and 0.5 to 1.0 µm, respectively. Whereas the supermicron region was observed in Fangcang Hospital Zone C PARR and Medical Staff's Office (Figure 1b and 1c) with 7 and 9 copies m -3 . The two concentration peaks in sub-and supermicron ranges have independent existence in SARS-CoV-2 aerosols and they do not necessarily co-exist indicating possible different formation mechanisms. The aerosol deposition sample collected from the Renmin Hospital ICU room had raw counts of SARS-CoV-2 RNA significantly above the detection limit as shown in Table S1 , although the TSP aerosol sample concentration inside this ICU room was below detection limit during the 3 hour sampling period. The much longer integration time of 7 days for the deposition sample has contributed to the accumulation of virus sediment. The area normalized deposition rate inside the ICU room is calculated to be 31 and 113 copies m -2 hour -1 . The sample with the higher deposition rate was placed in the hindrance-free corner of the room, approximately 3 meters from the patient's bed. The other sample recorded lower virus copies and it was placed in another corner with medical equipment above, and approximately 2 meters from the patient's bed. This may have blocked the path of virus aerosol sediment.