- The coronavirus may have spread through bathroom drains in a high-rise building in Guangzhou, China, a new study found.
- Researchers have detected the virus in human feces before.
- Now scientists think virus-laden feces particles could travel upward through an apartment building’s plumbing after a person flushes a toilet.
- But only certain conditions make this scenario possible, like poor ventilation.
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In February, three families in a high-rise building in Guangzhou, China, tested positive for the coronavirus. They didn’t know each other, didn’t live on the same floor, and hadn’t come into contact.
So scientists started to suspect that the virus had spread through the building’s plumbing.
Researchers know live coronavirus can be found in human feces and that the virus can spread via small airborne particles called aerosols. So it’s not surprising that flushing a toilet can release “bioaerosols” — coronavirus-laden poop particles — that could infect other people. What’s more surprising is that these particles seemed to travel across a 12-story gap between apartments in Guangzhou.
In a study published Tuesday, scientists traced the Guangzhou outbreak to a five-person family living on the 15th floor. Four of the family members had traveled to Wuhan, China, in January, while the coronavirus was spreading across the city.
Shortly after the family returned home, two middle-aged couples — one on the 25th floor and another on the 27th — started feeling sick as well. None of the other high-rise residents tested positive for the virus.
Footage showed that the families hadn’t shared an elevator while anyone was infectious, and there was no trace of the virus on the elevator button or in air ducts.
The scientists did find positive virus samples in the five-person family’s apartment, however — specifically in the master bathroom. So the researchers released ethane gas down the family’s toilet, then checked for that gas in the apartments above. All of the families were under quarantine at the time, so there was no opportunity for the virus to spread through close physical contact.
Sure enough, the researchers found ethane in the middle-aged couples’ apartments, as well as in two other apartments on the 16th and 21st floors. That’s evidence that bioaerosols might have traveled through the plumbing system. Residents on the higher floors may have inhaled the particles directly or touched surfaces where the particles had landed in their bathrooms.
Certain apartments were more susceptible than others
The coronavirus typically spreads via respiratory droplets after an infected person coughs, sneezes, or talks. Researchers aren’t sure about the degree to which the virus gets transmitted via aerosols, since the tiny particles are extremely hard to trap and study without killing the virus.
But a 2018 study showed that bioaerosols generally could linger in the air for 30 minutes or more after a toilet flush.
Researchers think certain environments favor airborne transmission, specifically poorly ventilated rooms. The risk goes down when a space is well-ventilated: According to a May study, the