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.

中文翻译：

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严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 通过空气传播的社区证据


背景 广州市一个社区观察到 9 例 COVID-19（2019 年冠状病毒病）病例。所有病例都居住在一栋建筑的三个垂直排列的单元中，共享同一管道系统，这为检查 SARS-CoV-2 的传播模式提供了一个独特的机会。方法对病例进行访谈，了解其旅行史和密切接触史。收集所有病例的呼吸道样本进行病毒系统发育分析。随后在建筑物内进行了模拟实验，并在类似建筑物内进行了并行控制实验，以研究通过空气传播的可能性。结果居住在15-b公寓的指数患者有武汉旅行史，居住在25-b、27-b公寓的4例病例随后确诊。系统发育分析显示，所有患者的病毒均来自同一病毒株。指示病例与其他家庭之间没有密切接触，表明传播可能不是通过飞沫和密切接触发生的。气流检测和模拟实验表明，冲厕所可以增加管道内气流的速度，并将气流从15-b公寓传输到25-b和27-b。受感染建筑物内排气流量的降低可能是导致疫情爆发的原因之一。结论 该社区COVID-19的爆发很大程度上是通过空气传播来解释的，未来的预防感染工作应考虑到通过空气传播的可能性。建筑设计中应考虑断开厕所的排水管和排气管，以防止病毒通过空气传播。