Coronavirus Disease 2019 Outbreak Likely Caused by Sewage Exposure in a Low-Income Community: Guangzhou, China, April 2020

Abstract

Background: SARS-CoV-2 has been identified in the feces of COVID-19 patients. However, fecal transmission has never been shown epidemiologically. In April 2020, a COVID-19 outbreak occurred in a low-income community in Guangzhou, China. We investigated this outbreak to identify the mode of transmission. Methods: 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. We conducted a retrospective cohort study among the residents living in the same building as the cases to identify transmission risk factors. Findings: We found eight cases (four couples) in this community of 2888 residents (attack rate=2.8/1000), with onset from April 5 to 21, 2020. During their incubation periods, Cases 1 and 2 frequented a Market T, where an outbreak was ongoing. Cases 3-8 never visited Market T during incubation periods, lived in separate buildings from, and never interacted with, Cases 1 and 2. Retrospective cohort study showed that working as cleaners or street scavengers (RR=13, 95% CI: 1.8-99), not changing to clean shoes after returning home (RR=7.4, 95% CI: 1.7-33), collating and cleaning dirty shoes after returning home (RR=6.3, 95% CI: 1.4-28) were significant exposure risk factors. Of 63 samples collected from street sewage puddles and sewage pipes, 19% tested positive for SARS-CoV-2. Of 50 samples taken from the cases’ apartments, 24% tested positive. RNA sequencing showed that the viruses identified from the squat toilet and the shoe-bottom dirt from the apartments of Cases 1 and 2 are homologous with those from Cases 3-8 and those identified from the sewage samples. The sewage pipe leading from the apartment of Cases 1 and 2 down to the drainage had a large crack above the ground. Rainfalls after the onset of Cases 1 and 2 flooded the streets. Interpretation: Our investigation has for the first time provided epidemiologic evidence that SARS-CoV-2 can be 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. Funding: No. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: This study was approved by the ethics committees of GZCDC (approval number GZCDC-ECHR-2020A0004).