key: cord-0713140-gnq3mnyx authors: Lin, Guozhen; Zhang, Shiyu; Zhong, Yi; Zhang, Lin; Ai, Siqi; Li, Kuibiao; Su, Wenzhe; Cao, Lan; Zhao, Yuteng; Tian, Fei; Li, Jinrong; Wu, Yinglin; Guo, Chongshan; Peng, Rongfei; Wu, Xinwei; Gan, Pingsheng; Zhu, Wei; Lin, Hualiang; Zhang, Zhoubin title: Community evidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission through air date: 2020-11-20 journal: Atmos Environ (1994) DOI: 10.1016/j.atmosenv.2020.118083 sha: aa6437f0913e0d6860e37b353b6c1278147a6a95 doc_id: 713140 cord_uid: gnq3mnyx BACKGROUND: Nine COVID-19 (Corona Virus Disease, 2019) cases were observed in one community in Guangzhou. All the cases lived in three vertically aligned units of one building sharing the same piping system, which provided one unique opportunity to examine the transmission mode of SARS-CoV-2. METHODS: We interviewed the cases on the history of travelling and close contact with the index patients. Respiratory samples from all the cases were collected for viral phylogenetic analyses. A simulation experiment in the building and a parallel control experiment in a similar building were then conducted to investigate the possibility of transmission through air. RESULTS: Index patients living in Apartment 15-b had a travelling history in Wuhan, and four cases who lived in Apartment 25-b and 27-b were subsequently diagnosed. Phylogenetic analyses showed that virus of all the patients were from the same strain of the virus. No close contacts between the index cases and other families indicated that the transmission might not occur through droplet and close contacts. Airflow detection and simulation experiment revealed that flushing the toilets could increase the speed of airflow in the pipes and transmitted the airflow from Apartment 15-b to 25-b and 27-b. Reduced exhaust flow rates in the infected building might have contributed to the outbreak. CONCLUSIONS: The outbreak of COVID-19 in this community could be largely explained by the transmission through air, and future efforts to prevent the infection should take the possibility of transmission through air into consideration. A disconnected drain pipe and exhaust pipe for toilet should be considered in the architectural design to help prevent possible virus spreading through the air. The building is a 29-storey apartment with three units (a, b, and c) on each floor, 120 except that the top floor (29 th floor) has two units (a and b) (Figure 1 ). Residents of 121 the same unit of different floors share one drain pipe, one sewer pipe and one exhaust 122 pipe. Normally, the three pipes are connected to each other and lead to the same vent 123 on the roof. But, the vent of the straight pipeline was replaced with a right-angle 124 bending one, and the diameter changed from 100 mm to 75 mm (Figure 1 ). The 125 pictures of the pipes in the community were shown in Figure S1 . and sewer pipe connected with floor drains was used to exhaust the sewage. Sewer 135 pipe and drain pipe were connected with the exhaust pipe by an H-shaped joint 136 respectively. This kind of design had better discharge capacities and was widely 137 adopted in high rise buildings. The same apartment vertical section shared the same 138 piping system (Guan, Fang et al. 2020 ). The same vertically aligned units shared the 139 same piping system. SARS-CoV-2 were synthesized as previously described (Chan, Yuan et al. 2020 We were unable to collect the samples in the elevators as they were disinfected and 175 Given that all the cases occurred in the same unit and that these households shared a 201 common pipe system, we therefore conducted a simulation experiment to investigate 202 the process of potential transmission through air. Dry drain means the water level in 203 the U-trap is lower than 0.5cm or the U-trap is empty and thus can't play a protective The mixture of chloroform and carbon tetrachloride was used to mimic the spread 209 process as they had not been used in these apartments before or existed in detergent 210 and paint. so that the measurement might not be influenced by the background level. 211 Considering that the chloroform and carbon tetrachloride with strong stimulate odor 212 and unhealthy nature, this experiment was conducted after all the residents from Unit 213 b were moved out of their apartments for quarantine. And the residents were allowed 214 to move back their apartments after more than 14 days ventilation. We Our retrospective inspection of the video records in the elevators suggested that a total 284 of 83 residents (28 from Unit b and 55 from non-Unit b) had taken the elevators after 285 the index patients from Family 1 used them (Table 1 ). In addition, we found that the 286 The results of wind speed after flushing the toilet were depicted in Table 2 and Table 3 . The results of the tracer-gas experiment were shown in Table 4 There is an increasing concern on the possibility of the SARS-CoV-2 transmission 361 through air, in this respect, our study provided the timely evidence from a field survey 362 in a community with an outbreak of SARS-CoV-2. The consistent findings from the 363 epidemiological investigation, the airflow experiment, the simulation experiment, as 364 well as the parallel control experiment, supported that the virus might be transmitted 365 by the contaminated air in some special circumstances. 366 In view of seriousness of this community outbreak, local government and the 367 department of health had timely clean and disinfect the apartment and promptly 368 transferred all the occupants to a hotel for quarantine. Meanwhile, with the 369 improvement of self-protection consciousness, residents had generally and 370 consciously worn the masks and avoided going outside. Thus, the outbreak was timely 371 stopped and did not cause a wider range of infection. However, the causes behind this 372 community outbreak deserve to pay enough attention and take warning. 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