COVID-19: SARS-CoV-2 Transmission Probable Through Fecal Aerosols

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may be transmitted through fecal aerosols, according to both a study and editorial recently published in the Annals of Internal Medicine.^1,2

The coronavirus disease 2019 (COVID-19) pandemic has led to a review of all building systems involving airflow and all procedures and systems that produce aerosols. There are 2 main groups of viral transmission: direct contact between an infected and a susceptible person, and indirect contact by a susceptible person with virus shed in droplets or aerosols from an infected person. This indirect transmission occurs when a susceptible person encounters surfaces or air that are contaminated with droplets or aerosols that contain infectious virus, and the virus is transferred to their mouth or nose or inhaled from environmental systems.²

Most authorities state that SARS-CoV-2 is transmitted mainly by close contact and fomites; however, there is increasing evidence that SARS-CoV-2 viral particles may shed in feces. Researchers from China investigated a case in which transmission through indirect contact occurred in an apartment building via particles carried on air streams within the pipe network that entered the interior of the building from the wastewater system.¹

This reported case involved an outbreak of 9 confirmed cases of COVID-19 in a high-rise apartment building (3 vertically aligned flats; block X) in Guangzhou, China, during a period of social distancing.¹ Block X includes 29 floors with 3 apartment flats on floors 2 through 28, and 2 flats on floor 29, for a total of 83 flats. In total, 9 infected patients, 193 other residents of the building, and 24 building management staff were included in the case.

Symptom onset dates and flat locations of the 9 residents with SARS-CoV-2 infection were obtained. All infections were confirmed via throat swab and RNA test results. Associated environmental variables were examined to verify the role of fecal aerosols, including closed circuit television footage used to assess the movement of the buildings’ occupants; 237 surface and air samples taken from 11 of the flats, public areas, and building drainage systems; and tracer gas that was released into bathrooms as a surrogate for virus-laden aerosols in the drainage system.

Results suggest that fecal aerosol transmission may have caused the community COVID-19 outbreak based on circumstantial evidence. The 9 infected patients included 3 families. The first family had history of travel to Wuhan, China, the epicenter of COVID-19; the other 2 families had no travel history and a later onset of symptoms. The families lived in 3 vertically aligned flats that were connected by drainage pipes in the master bathrooms. The observed infections and the locations of positive environmental samples are consistent with the vertical spread of virus-laden aerosols via these stacks and vents. There was no evidence found for transmission via the elevator or elsewhere.

Michael Gormley, PhD, of the Heriot-Watt University in Edinburgh, pointed out in his accompanying editorial that the study “add[s] to the growing body of evidence that wastewater plumbing systems, particularly those in high-rise buildings, deserve closer investigation, both immediately in the context of SARS-CoV-2 and in the long term, because they may be a reservoir for other harmful pathogens.”¹

References

1. Kang M, Wei J, Yuan J, et al. Probable evidence of fecal aerosol transmission of SARS-CoV-2 in a high-rise building [published online September 1, 2020]. Ann Intern Med. doi: 10.7326/M20-0928
2. Gormley M. SARS-CoV-2: the growing case for potential transmission in a building via wastewater plumbing systems [published online September 1, 2020]. Ann Intern Med. doi: 10.7326/M20-6134