Spread of SARS-CoV-2 aerosols via two connected drainage stacks in a high-rise housing outbreak of COVID-19

Qun Wang, Zhang Lin, Jianlei Niu, Garnet Kwan Yue Choi, Jimmy C.H. Fung, Alexis K.H. Lau, Peter Louie, Kenneth K.M. Leung, Jianxiang Huang, Pan Cheng, Pengcheng Zhao, Wenzhao Chen, Sheng Zhang, Liye Fu, P. W. Chan, Ann Han Wong, Herman Tse, Sally Cheuk Ying Wong, Raymond Wai Man Lai, David SC HuiKwok Yung Yuen, David Christopher Lung, Yuguo Li

Research output: Journal article publicationJournal articleAcademic researchpeer-review

20 Citations (Scopus)


Vertical transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) along a vertical column of flats has been documented in several outbreaks of coronavirus disease 2019 (COVID-19) in Guangdong and Hong Kong. We describe an outbreak in Luk Chuen House, involving two vertical columns of flats associated with an unusually connected two-stack drainage system, in which nine individuals from seven households were infected. The index case resided in Flat 812 (8th floor, Unit 12), two flats (813, 817) on its opposite side reported one case each (i.e., a horizontal sub-cluster). All other flats with infected residents were vertically associated, forming a vertical sub-cluster. We injected tracer gas (SF6) into drainage stacks via toilet or balcony of Flat 812, monitored gas concentrations in roof vent, toilet, façade, and living room in four of the seven flats with infected residents and four flats with no infected residents. The measured gas concentration distributions agreed with the observed distribution of affected flats. Aerosols leaking into drainage stacks may generate the vertical sub-cluster, whereas airflow across the corridor probably caused the horizontal sub-cluster. Sequencing and phylogenetic analyses also revealed a common point-source. The findings provided additional evidence of probable roles of drainage systems in SARS-CoV-2 transmission.

Original languageEnglish
Article number128475
JournalJournal of Hazardous Materials
Publication statusPublished - 15 May 2022


  • Airflow
  • COVID-19
  • Drainage system
  • SARS-CoV-2
  • Stack aerosol

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution
  • Health, Toxicology and Mutagenesis


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