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Computer models developed by a trio of researchers in China suggest flushing a toilet can produce a cloud of virus-containing aerosol droplets.
Several studies have shown that COVID-19 particles persist in the stool of infected patients, whether or not the patients present with gastrointestinal symptoms.
The latest research, published Tuesday in the journal Physics of Fluids, suggests that if coronavirus particles can find their way into toilets, flushing can aerosolize them.
"In my opinion, if the fecal-oral transmission is true, the toilet-borne viral cloud particles should be a source of the spread of COVID-19," corresponding author Ji-Xiang Wang, researcher at Yangzhou University, told UPI in an email.
Researchers augmented a pair of previously designed fluid dynamic models to simulate movement of the numerous tiny droplets likely to be expelled into the air by a flushed toilet.
Scientists simulated the aerosolization of virus particles by two types of toilets: one with a single inlet for flushing water and another with two inlets that produce a rotating flow.
Simulations showed both toilets produced enough vertical velocity to create a cloud of aerosolized virus particles. According to the computer models, flushing could propel aerosols as high as three feet above the toilet seat, where they could be inhaled or settle on surfaces.
While there is mounting evidence that fecal-oral transmission of COVID-19 is possible, there is yet to be any conclusive epidemiological evidence that fecal-oral transmission is aiding the global spread of the novel coronavirus.
But the authors of the latest paper think public health officials should take the possibility of fecal-oral transmission seriously.
"The authors want to send messages to the average people that the flushing will lift the virus up from the toilet bowl so they need to close the lid first and then trigger the flushing process," Wang said.
"If the flushing is an automatic process without closing the lid, we should wash our hands carefully," Wang said. "The toilet manufacturers should design a new toilet in which the lid is automatically put down before flushing. Automatic cleaning should also be added, especially for the public toilet."