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Clin Infect Dis
. 2020 Oct 12;ciaa1494.
doi: 10.1093/cid/ciaa1494. Online ahead of print.
Sewage as a Possible Transmission Vehicle During a Coronavirus Disease 2019 Outbreak in a Densely populated Community: Guangzhou, China, April 2020
Jun Yuan 1 , Zongqiu Chen 1 2 , Chenghua Gong 3 , Hui Liu 1 , Baisheng Li 1 , Kuibiao Li 1 , Xi Chen 1 , Conghui Xu 1 , Qinlong Jing 1 , Guocong Liu 3 , Pengzhe Qin 1 , Yufei Liu 1 , Yi Zhong 1 , Lijuan Huang 3 , Bao-Ping Zhu 4 , Zhicong Yang 1
Affiliations
- PMID: 33043972
- DOI: 10.1093/cid/ciaa1494
Abstract
Background: SARS-CoV-2 has been identified in the fecal matter of COVID-19 patients. However, sewage transmission has never been shown. In April 2020, a COVID-19 outbreak occurred in a densely populated community in Guangzhou, China. We investigated this outbreak to identify the mode of transmission.
Method: A home quarantined order was issued in the community. We collected throat swab samples from the residents and environmental samples from the surfaces inside and around the houses, and conducted RT-PCR testing and genome sequencing. We defined a case as a resident in this community with a positive RT-PCR test, with or without symptoms. We conducted a retrospective cohort study of all residents living in the same buildings as the cases to identify exposure risk factors.
Result: We found eight cases (four couples) in this community of 2888 residents (attack rate=2.8/1000), with onset during April 5-21, 2020. During their incubation periods, Cases 1-2 frequented market T with an ongoing outbreak. Cases 3-8 never visited market T during incubation period, lived in separate buildings from, and never interacted with, Cases 1-2. Retrospective cohort study showed that working as cleaners or waste picker (RR=13, 95% CIexact: 2.3-180), not changing to clean shoes after returning home (RR=7.4, 95% CIexact: 1.8-34), collating and cleaning dirty shoes after returning home (RR=6.3, 95% CIexact: 1.4-30) were significant exposure risk factors. Of 63 samples collected from street-sewage puddles and sewage-pipe surfaces, 19% tested positive for SARS-CoV-2. Of 50 environmental samples taken from cases' apartments, 24% tested positive. Viral genome sequencing showed that the viruses identified from the squat toilet and shoe-bottom dirt inside the apartment of Cases 1-2 were homologous with those from Cases 3-8 and those identified from sewage samples. The sewage pipe leading from the apartment of Cases 1-2 to the drainage had a large hole above ground. Rainfalls after the onset of Cases 1-2 flooded the streets.
Conclusion: Our investigation has for the first time pointed to the possibility that SARS-CoV-2 might spread by sewage. This finding highlighted the importance of sewage management, especially in densely-populated places with poor hygiene and sanitation measures, such as urban slums and other low-income communities in developing countries.
Keywords: COVID-19; SARS-CoV-2; disease outbreak; epidemiology; infectious disease transmission; risk factor; sewage management.