Examination of a mask in public toilets should be mandatory during the pandemic, researchers say, as there is growing evidence that flushing toilets – and now urinals – can release harmful particles of coronavirus into the air.
The coronavirus can be found in a person’s urine or stool, and flushing urinals can generate an “alarming upward flow” of particles that “travel faster and fly farther” than particles from a toilet flush, according to a study published in the journal Physics of Fluid Monday.
“Urinary incontinence actually promotes the spread of bacteria and viruses,” researcher Xiangdong Liu said in a press release. “Wearing a mask should be mandatory in public restrooms during the pandemic, and anti-proliferation improvements are urgently needed to prevent the spread of COVID-19.”
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Liu and other researchers from Yangzhou University in China simulated urination rinsing with computer models and estimated that, within just five seconds of rinsing, virus particles can reach a height of more than 2 feet from the ground.
“Potentially, it could contaminate other surfaces you would touch – the handle, the tap,” said Charles Gerba, a professor of virology at the University of Arizona. “The concern is, too – was there anything left of the person who was there before? Aerosolization of the previous user that you could potentially catch up with?”
Some of the same researchers published similar findings in June, focusing on toilet flushes. Through another computer model, the researchers found that thousands of particles could escape from the toilet within 70 seconds of flushing, and that some could reach more than a foot above the toilet in half the time.
“It is reasonable to assume that the high-velocity airflow will expel aerosol particles from the basin to regions high in the air above the toilet, allowing viruses to spread inside posing risks to human health,” the researchers said at the time.
The studies are interesting, but not surprising, because research into refurbished particles in “toilet feathers” has now been going on for almost two decades, said Joshua Santarpia, a professor of pathology and microbiology at the University of Nebraska Medical Center specializing in bioaerosols.
“The more interesting thing for me was that I had not considered the urinary problem – whether SARS-CoV-2 is excreted in urine,” he said.
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Many people are unaware that toilets and urinal particles can be released into the air, let alone that genetic material from SARS-CoV-2 – the virus that causes the disease known as COVID-19 – can be found in the urine and stool of patients, Gerba said.
“It’s probably overdone – contamination of urine,” Gerba said. “Smallpox, Zika virus are excreted in the urine. What is surprising is that a respiratory virus can be excreted in the urine.”
At least two studies – one in Tokyo and one in Guangzhou, China – have found coronavirus RNA in patients’ urine. Studies published in the journals Gastroenterology and The Lancet also found coronavirus RNA in patients’ crutches, even weeks after the patients showed negative results in respiratory samples. However, one study in and around Beijing found no evidence of virus in 72 urine specimens.
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It is still unclear whether COVID-19 can be transmitted through urine and infect another person, Gerba said.
“Is there enough virus in the urine to worry you? Is it aerosolized enough? Those are questions we need to look at,” he said.
Yangzhou University researchers claim that transmission in a public restroom has already taken place. She cited local news reports of a couple, who work at a food market in Beijing, and contracted the virus at a nearby toilet.
“What’s worse, two of COVID-19’s reaffirmative cases in Beijing have been reported to be infected from a public toilet, which practically proves the danger from the public toilet, ‘the investigators wrote.
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Health experts believe the virus is transmitted primarily through respiratory droplets when someone coughs or sneezes, but the World Health Organization says “short-range aerosol transmission … can not be ruled out.”
Researchers measuring the number of viral aerosols in different areas of two Wuhan hospitals found that although the concentration detected in isolation homes and ventilated patient rooms was very low, it was higher in the toilet areas used by the patients, according to an April study published in the journal Nature.
The researchers recommend that room ventilation, open space, sanitation of protective clothing, and proper use and disinfection of toilet areas can effectively limit the concentration of SARS-CoV-2 RNA in aerosols.
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“I think there are a lot of strategies and interventions that can be developed if it really does show that there is significant risk,” Gerba said.
For now, the next best step would be to put the researchers’ computer model to the test to see if playing a urinal actually traps virus particles in the air, Gerba and Santarpia said.
“Someone really needs to validate this experiment. It’s a model, and there are a lot of assumptions,” Santarpia said. “More work needs to be done.”
Follow Grace Hauck on Twitter at @grace_hauck.
