Close the Lid! Flushing Toilets Spreads Coronavirus

Modesto Morganelli
Июня 17, 2020

Computer models developed by a trio of researchers in China suggest flushing a toilet can produce a cloud of virus-containing aerosol droplets.

Research has found SARS-CoV-2, the virus that causes COVID-19, in people's gastrointestinal tract as well as stool samples from infected patients, meaning that the virus could possibly spread from fecal-oral transmission.

Chinese scientists calculate that flushing can propel a plume of spray up and out of the toilet bowl, reaching head height and beyond. The public, however, remains largely unaware of this infection pathway, since few quantitative studies have been carried out to investigate this possible mechanism.

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. The simulations included two types of toilets - one with a single inlet for flushing water, and another with two inlets for water to create a rotating flow.

"The big unknown is how much virus is infectious in the toilet when you flush it ... and how much virus does it take to cause an infection", Gerba told the newspaper. Wang also recommends washing your hands frequently and carefully, especially if you are using a public bathroom. A similar model was used recently to simulate the movement of aerosol droplets ejected during a human cough. These vortices continue upward into the air above the bowl, carrying droplets to a height of almost 3 feet, where they might be inhaled or settle onto surfaces. These droplets float in the air for more than a minute, the researchers found. A toilet with two inlet ports for water generates an even greater velocity of upward flowing aerosol particles.

Ji-Xiang Wang, who studies fluid dynamics at Yangzhou University and a co-author of the study, told The New York Times that she hopes bathroom design will be improved and that there will be more contactless soap dispensers and paper towels. Toilets with two ports create an even greater velocity of aerosol particles; simulations showed that with two-port toilets, almost 60% of aerosol particles rise above the seat (for single-port toilets, that figure was around 40%). A solution to this deadly problem is to simply close the lid before flushing, since this should decrease aerosol spread.

"[We] 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". Scientists say they should also keep their mask on inside the bathroom and avoid touching their face while inside.

A new study conducted warns people that the coronavirus could be transmitted through flushing the toilet while the lid is up.

Reference: "Can a toilet promote virus transmission?"

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