Can corona virus spread through sewage pipes of an apartment building?

Virus can also be found in human faeces -- several days after the patient has tested negative for the respiratory symptoms of COVID-19. Viral shedding from the digestive system can last longer than shedding from the respiratory tract. Therefore, this could be an important -- but as yet unquantified -- pathway for increased exposure (1).

In the year 2020, health officials in Hong Kong partially evacuvated from an apartment block over fears of corona virus may have been transmitted via the building's pipes. Two residents living on different floors of a high-rise tower called Hong Mei House, in northwestern Hong Kong's Tsing Yi, had been infected with coronavirus, health officials said. A 62-year-old woman was diagnosed with the virus about a week-and-a-half after a 75-year-old man in the same building became infected.Three more cases have since been linked to Hong Mei House. The woman's son, his wife and her father have been diagnosed with the virus. The mother, son and wife share an apartment (2).

Liquid aerosols don’t stay liquid forever. Some droplets fall onto surfaces, but over time, when they stay airborne for long enough, the water evaporates and they become droplet nuclei. These droplet nuclei are small, dry particles that are light and can remain airborne for long periods of time. Aerosols, whether they’re generated from a person’s cough or a flushed toilet, can carry bacteria or viruses.

Fecal aerosols carrying SARS-CoV-2 could have traveled through the drains in an apartment block in China and infected unrelated people in different apartments.

Scientists haven’t found direct evidence that toilet aerosols can spread viral diseases, but they have been studying the germy plumes caused by flushed toilets since at least the 1950s. Over time, they have refined their experimental setups to try to get a more accurate picture of how infectious the aerosols might be (3).

More and more people are now complaining that they have tested positive despite being locked up in their homes without any physical contact with the outer world. Could one reason be your faulty bathroom sewage pipe?

Listen to what the experts say:

There is some work work on the Q you asked.

As the waste water go down the pipe line, and as aerosols can’t reach very high -unless the pipes are extremely dry- through a sewage pipe, it is highly unlikely that they can contaminate the sewage pipes upstairs. Moreover, the water running down from upstairs might also remove whatever little contamination is present. Therefore, people living upstairs might not get the infection through the sewage pipelines from the people living downstairs. But, he have a story from China that says even this is possible.

All five members of a family living in a 15th floor apartment tested positive for SARS-CoV-2 in late January, after most of them had visited Wuhan, where the pandemic started. A few days later, two middle-aged couples living on the 25th and 27th floors—part of a stack of vertically arranged apartments directly above the flat in question and all sharing the same waste pipes—became ill. They had not traveled or been in close contact with a sick person during China’s lockdown.

A research team compiled a range of evidence suggesting the two couples were exposed to fecal aerosols from their neighbors more than 10 floors below through their shared waste pipes. Camera footage from elevators indicated that the families did not cross paths. Among more than 200 air and surface samples collected in the high-rise in mid-February, the only ones testing positive for SARS-CoV-2 came from the 15th floor family’s apartment and a vacant apartment’s bathroom on the 16th floor directly above. Finally, a tracer gas that the team piped into the 15th floor apartment’s drainpipe exited in the 25th and 27th floor apartment bathrooms (4). The researchers could not verify that any of the three U-shaped traps in the apartments had dried out when the COVID-19 cases happened, however. The apartments had already been cleaned and the traps filled with water when they visited. Evidence for spread via plumbing remains “circumstantial,” according to them.

People living downstairs might easily get infected from people living upstairs through drainage pipes. Flushing a toilet can spew viral particles far above the seat. A person could therefore be exposed to SARS-CoV-2 by breathing aerosolized fecal matter that entered his toilet through the pipes, but the chances are very low.

But researchers say the risk should not be ignored. Because….

Amoy Gardens, a Hong Kong housing complex with multiple apartment towers, saw 321 residents catch SARS in 2003; 42 of them died. Researchers traced the outbreak to a single visitor with SARS who had severe diarrhea. The bathrooms in the apartments had floor drains for cleaning, and when the U-shaped traps beneath these drains dried out, aerosolized SARS virus from the sick resident reached apartments through an air shaft. Typically, such wafting is blocked by water that has accumulated in the traps. Scientists even think the wind even carried the aerosols to adjacent buildings.

The travel path of aerosols depends on many factors and may be impossible to prove, researchers say. A sick person would have had to produce lots of infectious virus, which would have had to reach others quickly and at a high dose. It would also depend on a building’s plumbing system and how well it is maintained.

So the experts give this advise: good hygiene is essential to stop the spread—washing hands, cleaning the toilet, and keeping the lid down when flushing. If you live in a high-rise apartment building, make sure U-shaped traps are filled—that’s easily done by regularly running water in tubs and sinks. But gases can also leak from aging pipes. So, if you can smell the drain odour in your bathroom, do something. And don’t go anywhere near the spaces where drainage pipes are located like the ducts.

How aerosols spread in toilets....

Footnotes : 

1. http://Richard S. Quilliam, Manfred Weidmann, Vanessa Moresco, Heather Purshouse, Zoe O'Hara, David M. Oliver. COVID-19: The environmental implications of shedding SARS-CoV-2 in human faeces. Environment International, 2020; 105790 DOI: 10.1016/j.envint.2020.105790
2. How can the coronavirus spread through bathroom pipes?
3. https://cen.acs.org/biological-chemistry/infectious-disease/COVID-1...
4. Can you catch COVID-19 from your neighbor’s toilet?