Broken sewage pipe might have caused small COVID-19 outbreak in China
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Epidemiologic evidence indicates that a broken sewage pipe might have been the cause of a small outbreak of COVID-19 in a Chinese city, researchers recently reported.
“The SARS-CoV-2 virus has been identified in the fecal matter of infected patients and in sewage before. However, this study for the first time provided epidemiologic evidence that sewage can serve as a transmission vehicle, leading to outbreaks,” Bao-Ping Zhu, MD, PhD, an independent scholar, told Healio.
Zhu and colleagues collected throat swab samples and environmental samples from homes in a community in Guangzhou, China, that had experienced a COVID-19 outbreak. They defined a COVID-19 case as an individual from the community with a positive PCR test with or without symptoms. They also conducted a retrospective analysis of all individuals living in the same building to find potential exposure risk factors.
The researchers discovered eight cases within the community of 2,888 residents — an attack rate of 2.8 cases per 1,000 people. An inspection revealed that a sewage pipe in the home of two of the infected individuals had a hole that spilled into five drains connected to the surrounding buildings that the other six infected individuals lived in, and also soaked the entrances of two of the buildings. Zhu and colleagues hypothesized that these six individuals were infected via leaked sewage.
According to the researchers, exposure history and dates of symptom onset indicated that the six patients were not likely to have been infected directly by the initial cases. However, working as a waste picker or cleaner was significantly associated with risk for infection (RR = 13; 95% CI, 2.3-180), as was not changing shoes (RR = 7.4; 95% CI, 1.8-34) when returning home and not cleaning dirty shoes (RR = 6.3; 95% CI, 1.4-30). Moreover, the researchers matched the virus from the last six cases to the virus found inside the home of the first two patients. They reported that “the spatial distribution of [the six cases was] consistent with the direction of the sewage flow.”
No more infections were reported after the leak was fixed, they said.
“SARS-CoV-2 has been thought to be unable to survive in the harsh conditions of the sewage. It was surprising that this virus not only could survive in sewage but was capable of causing outbreaks,” Zhu said. “The main limitation was that no viable SARS-CoV-2 was found by virus culture. However, the epidemiologic evidence from this study was strong.”
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