Sewage as a Possible Transmission Vehicle During a Coronavirus Disease 2019 Outbreak in a Densely Populated Community: Guangzhou, China, April 2020

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.

Letter to the Editor regarding Mathavarajah et al. (2020) Pandemic danger to the deep: The risk of marine mammals contracting SARS-CoV-2 from wastewater

“…We agree that the potential for transmission of SARS-CoV-2 via the fecal-oral route exists, but we would like to highlight that current data suggests that this risk is low and mainly relevant in areas where sanitation and hygiene are compromised and exposure to fresh feces is expected ( Jones et al, 2020 ). This is supported by the recent work by Yuan et al (2020) , which epidemiologically linked fresh sewage and faulty plumbing in an outbreak, similar to what happened with the SARS-CoV-1 Amoy Gardens outbreak. Yuan et al recommended regular inspection and maintenance of plumbing systems to limit transmission of SARS-CoV-2 in densely populated areas; a recommendation that aligns with other authors ( Gormley et al, 2020 ).…”

“…Yuan et al recommended regular inspection and maintenance of plumbing systems to limit transmission of SARS-CoV-2 in densely populated areas; a recommendation that aligns with other authors ( Gormley et al, 2020 ). Interestingly, Yuan et al (2020) also reported that they were unable to provide direct evidence of sewage transmission because cell culture assays of clinical and environmental samples were negative. This corresponds with recent studies that have shown that the colonic environment is inhospitable for new SARS-CoV-2 virions released into the intestinal lumen ( Zang et al, 2020 ; Wölfel et al, 2020 ).…”

Potential discharge, attenuation and exposure risk of SARS-CoV-2 in natural water bodies receiving treated wastewater

“…The awareness of the potential risk of SARS-CoV-2 from wastewater has increased since RNA detection of SARS-CoV-2 in wastewater reached public domains 3,[10][11][12] . Recently, possible transmission of COVID-19 from sewage was reported by a cohort study in Guanzhou, China 13 . Although the occurrence of fecal-oral route transmission and infectivity of SARS-CoV-2 in wastewater is still controversial, there are growing concerns about the exposure risk of SARS-CoV-2 in natural water bodies that receive treated effluent from wastewater treatment plants (WWTPs), among citizens, administrative sectors, and policymakers.…”

A New Transmission Route for the Propagation of the SARS-CoV-2 Coronavirus

“…The versatility of the virus tropism, in addition to interfering with the immune response, may induce an additional propagation route depending on virus tropism; contagion may involve a variety of causes, such as environments contaminated with virus carrier secretions, dirty water effluents, besides the expected direct contamination via aerosols. This means that the orofecal route should be considered as an important complement of contact with the virus (see [ 11 ] for recent information that sustains this hypothesis).…”