Flushing a Toilet Can Release Viral Droplets: What to Know

  • A new study finds that toilet flushing can cause virus particles to go into the air.
  • But the study was just a computer simulation, so there’s no reason to panic.
  • Maintaining physical distancing, wearing a mask, and washing your hands remain the best ways to avoid COVID-19.

Many states have begun reducing COVID-19 restrictions by opening up businesses, and recreational areas like parks and playgrounds. This means increased use of public bathrooms — an iffy proposition at the best of times.

Previous research suggests that the novel coronavirus can survive in the fecal matter of a person with COVID-19, and one recent Chinese study indicates that the virus might be spread by water from a flushing toilet.

But this is not a reason to panic if you have to use a public restroom. Here’s why.

Study findings rely on a simulation

A study co-author explained that this study was conducted during China’s lockdown for COVID-19 — a factor that significantly reduced the resources available to them.

“The outbreak of novel coronavirus occurred in China earlier this year and I was isolated in home according to the government regulation,” co-author Dr. Ji-Xiang Wang of Yangzhou University, China, told Healthline. “Therefore, I have limited resources of research in my university.”

Wang said, being stuck at home, he began to consider how fluid dynamics might influence virus spread — especially from toilets.

“When I used the toilet at that time and found significant vortex inside and I think maybe it may cause a massive spread of the virus,” said Wang.

Having lots of time and a computer at home, he said he decided to tackle the problem using a two-dimensional simulation.

Flushing creates droplets

According to the study, as water pours into the toilet bowl from one side, it strikes the opposite side to create vortices (whirlpools).

Researchers found that droplets in these vortices can rise above the bowl, carrying droplets up to 3 feet in the air, where they could be inhaled or contaminate surfaces.

Wang and team used computational fluid dynamics to “explore and visualize the characteristics of fluid flow during toilet flushing,” and analyzed how flushing could influence the spread of virus aerosol particles.

“According to the characteristics of fecal-oral transmission, there will be a large amount of viruses within a toilet when a confirmed case uses it. Thus, toilets should be regarded as one of the infection sources,” study authors wrote.

Findings showed that almost 60 percent of the droplets rise even higher above the seat for certain toilets. However, the study also finds that a solution to this problem is to close the lid before flushing, which should decrease aerosol spread.

But in the United States, toilets in public restrooms often don’t have lids.

The researchers write that one solution could be designing public toilets with automatically closing lids.

Do you need to worry?

It’s important to remember that Wang’s study is a computer simulation, and no observations were made in the “real world.”

The study was significantly limited by quarantine measures in place at the time.

“Yes, it has limitations,” Wang said. “I had limited resources of research when everything shut down at that time. I used a two-dimensional simulation where only vertical vortex was observed.”

“As everything begins to return normal in China and I have had the access to the high-performance computer in my lab, I think I will do the three-dimensional simulations later,” he added.

According to the Centers for Disease Control and Prevention (CDC), “No studies have yet clearly demonstrated or refuted toilet plume-related disease transmission, and the significance of the risk remains largely uncharacterized.”

“I have not heard of COVID-19 transmission from a flushing toilet,” admitted Dr. Nikhil Bhayani, an infectious disease physician with Texas Health Resources.

In other words, there is no evidence that this has occurred, or is (yet) recognized as a significant risk factor for transmission of COVID-19.

Evidence still supports coughing and sneezing as the primary ways that the virus is passed from one person to another.

How to stay safe when using public bathrooms

While droplets rising from a flushed toilet may not infect you, this doesn’t mean toilets, public or private, are completely safe.

Aerosols generated by someone with the coronavirus when they cough, sneeze, or talk can settle on surrounding surfaces, like bathroom sinks.

Research finds that the virus can survive for some time on various surfaces. To stay healthy, be careful, and touch as little as possible in public toilets, including taps and door handles.

Bhayani said although no disease is associated with toilets, bacteria or enteric viruses can be spread after touching a toilet and not washing hands. “The standard precautions include washing your hands after using a public toilet,” he said. He also emphasized that these bathrooms should be kept clean and in good working order to reduce this risk.

Keeping hand sanitizer and disinfectant wipes handy can help you be prepared, especially if the facilities lack soap or a working sink.

According to a spokesperson for the CDC, although “some spread may happen by touching the contaminated surface and touching the eye, nose, and mouth,” we should remember that “this [virus] does not last long on surfaces.”

The bottom line

New research using a computer simulation finds that flushing toilets can potentially spray coronavirus droplets far enough to increase COVID-19 risk.

Because the researchers were under lockdown, the study could only be conducted two-dimensionally on the computer.

Experts say there is no evidence that anyone has developed COVID-19 by droplet spray from a toilet. They also say the best way to reduce infection risk from a bathroom is to wash hands thoroughly afterward and touch the fewest surfaces possible.

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