A community outbreak of coronavirus in a high-rise apartment building is believed to have been caused by ‘fecal fumes’ that travelled through a drain pipe from a COVID-infected neighbour, a study has found.
Residents of the apartment building in Guangzhou, China, became the centre of a study published by the Annals of Internal Medicine after nine individuals from three families returned positive tests.
In total, 193 residents and 24 staff members of the building were tested and found the nine positive cases were vertical neighbours; they lived above one another.
The first family in the bottom apartment, identified in the study as ‘Family A’, had travelled to Wuhan in early January, while Families B and C had no travel history and a later onset of symptoms, according to the study.
The five members of Family A had returned home on January 24. On February 1, the middle-aged couple of Family B noticed an onset of COVID-19 symptoms. The families did not know each other and had not shared elevators during the infectious period.
Researchers used ethane as a tracer gas to test the pipes to the three apartments and found they were all connected by drainage stacks with a vent in the master bathrooms, which were aligned on each floor.
After continuously releasing the tracer gas in Family A’s master bathroom, concentrations of the gas were detected in all the other flats, demonstrating the pipes could serve as a “transport route” for bioaerosols, the study found.
Researchers found it likely that the infection in the building stemmed from three young members of Family A, and when these ‘index patients’ used and flushed the toilet, virus-laden particles would leak into other rooms via the drainage system.
If residents of the two units above Family A happened to be in their bathroom at the same time that the index patient flushed, researchers also believe it is possible that they may have inhaled the fumes.
“The bioaerosolization of wastewater mixed with urine, feces, and exhaled mucus originating from index patients is suggested to be the source of infectious bioaerosols in this outbreak,” the study found.
“Thus, the COVID-19 outbreak in block X may have been caused by fecal aerosol transmission, on the basis of circumstantial evidence.”
Medical Journal Australia editor in chief, Nick Talley, commented on the study in a tweet, saying it was interesting but speculative.
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