It may be the crappiest way to catch the coronavirus.
Researchers at Yangzhou University in China have used a computer simulation to show how flushing a toilet can spew a plume of virus-laden aerosol droplets as high as three feet — lingering in the air for up to a minute and possibly infecting others, according to the SciTechDaily.
Recent studies have shown that the virus that causes COVID-19 can survive in the digestive system and end up in the feces, raising the possibility that it could be transmitted from the toilet.
The bottom line: Close the lid before flushing.
“One can foresee that the velocity will be even higher when a toilet is used frequently, such as in the case of a family toilet during a busy time or a public toilet serving a densely populated area,” study co-author Ji-Xiang Wang, who teaches fluid dynamics at the school, said in a statement.
Toilet flushing generates strong turbulence, which researchers believe can spread both viruses and bacteria into the air.
The scientists, whose study was published in the journal Physics of Fluids, used computer models to simulate water and airflow in a flushing toilet — and the ensuing droplet cloud, the Chinese SciTechDaily reported.
They used a standard set of fluid dynamic formulas called Navier-Stokes equations to simulate flushing in two types of toilet — one with a single inlet for flushing water and the other with two inlets to generate a rotating flow.
The investigators also simulated movement of the tiny droplets likely to be ejected from the toilet bowl. A similar model has been used to simulate the movement of droplets ejected during a person’s cough.
The striking results showed that as water pours into the bowl from one side, it hits the opposite side, creating vortices that carry droplets to a height of about 3 feet for a minute, giving them time to be inhaled or settle on surfaces.
A toilet with two inlet ports generates an even greater velocity of rising aerosol particles, the researchers found. The simulations show that almost 60 percent of the ejected matter rises high above the seat for a toilet with two inlet ports.
Researchers have already suggested that toilets might provide a way for the bug to spread.
“Evidence of SARS-CoV-2 contamination of surface and air samples outside of isolation rooms, and experimental data showing that SARS-CoV-2 can live in aerosols for 3 hours, should raise concerns about this mode of transmission and prompt additional research,” Carmen McDermott of the University of Washington School of Medicine and colleagues wrote in April in the Journal of Hospital Infection, CNN reported.
“Fecal shedding seems to occur in patients without gastrointestinal symptoms, which could enable asymptomatic individuals with no respiratory symptoms to be a source of fecal transmission,” they said.
Bryan Bzdek, an aerosol researcher at Britain’s University of Bristol who was not involved in the latest study, said in a statement: “The viral load in fecal matter and the fraction of resulting aerosol containing the virus is unknown.
“Even if the virus were contained in the produced aerosols, it is unknown whether the virus would still be infectious; there is not yet clear evidence for fecal-oral transmission,” he said, according to CNN.
“The study authors suggest that whenever possible we should keep the toilet seat down when we flush, clean the toilet seat and any other contact areas frequently, and wash our hands after using the toilet,” Bzdek added.
“While this study is unable to demonstrate that these measures will reduce transmission of the SARS-CoV-2 virus, many other viruses are transmitted though the fecal-oral route, so these are good hygiene practices to have anyway.”