Experts have urged the public to flush the toilet with the lid down to help stem the spread of the coronavirus.
The previously-unknown strain mainly spreads face-to-face via infected droplets expelled in a cough or sneeze, however, there is evidence it is also transmitted in faeces.
Recent research found flushing a toilet releases up to 80,000 microscopic droplets into the air, which can float one metre (3.2ft) above the WC.
Scientists have previously warned of the risks of “toilet plume” in “the transmission of infectious diseases”.
One expert said closing the toilet lid before you flush is a “very easy way” to help stem the coronavirus outbreak.
Early research suggests the infection is mild in four out of five cases, however, it can trigger a respiratory disease called COVID-19.
The coronavirus is thought to have emerged at a seafood and live animal market in the Chinese city Wuhan at the end of last year.
It has since spread into more than 180 countries across every inhabited continent.
Latest coronavirus news, updates and advice
Since the outbreak was identified, more than one million cases have been confirmed, of whom over 221,600 have “recovered”, according to Johns Hopkins University.
Incidences have been plateauing in China since the end of February, and the US and Europe are now the worst-hit areas.
The UK has had more than 38,600 confirmed cases and over 2,900 deaths.
Globally, the death toll has exceeded 55,100.
Coronavirus: Does it spread in faeces?
Fears the coronavirus may spread via faecal matter arose in mid-February when two people living 10 floors apart in the same Hong Kong apartment block were diagnosed.
Officials later found an unsealed pipe in one of the patient’s bathroom, which could have allowed the virus into her flat.
The coronavirus is one of seven strains of a virus class that are known to infect humans.
Others trigger the common cold, while one leads to severe acute respiratory syndrome (Sars), which killed 774 people during its 2002/3 outbreak.
The new coronavirus is said to be more genetically similar to Sars than any other strain of that class.
In 2003, 342 people were diagnosed with Sars, of whom 42 died, in a 50-storey apartment block in Hong Kong.
The World Health Organization concluded “inadequate plumbing” was a “likely contributor”.
“Virus rich excreta” was thought to have “re-entered residents’ apartments” via “sewage and drainage systems where there were strong upward air flows, inadequate ‘traps’ and non-functional water seals”.
While the coronavirus may shed in human waste, some experts have questioned whether these traces are infectious.
“It isn’t a very pleasant thought, but every time you swallow, you swallow mucus from your upper respiratory tract,” said Dr John Edmunds from the London School of Hygiene & Tropical Medicine.
“This sweeps viruses and bacteria down into our gut, where they are denatured in the acid conditions of our stomach.
“With modern, very highly sensitive detection mechanisms we can detect these viruses in faeces.
“Usually, viruses we can detect in this way are not infectious to others, as they have been destroyed by our guts.”
Unlike with Sars, diarrhoea is not a common symptom of the new coronavirus, suggesting human waste is not a main route of transmission.
Coronavirus: Could flushing with the toilet lid down help stem the spread of infection?
Professor Qingyan Chen from Purdue University told Forbes there’s one “very easy way to help prevent the spread of the coronavirus.
“Close the lid and then flush.”
He claimed this prevents up to 80% of the particles that would otherwise escape from human waste into the air.
Boris Johnson has enforced draconian measures that require Britons to stay in their home, leaving only for “very limited purposes”, like shopping for essentials.
Anyone with the tell-tale fever or cough has been told to self-isolate entirely for seven days, while other members of their household must do so for two weeks.
Professor Chen recommended waiting one-to-two minutes after somebody else uses the toilet.
Official government guidelines urge suspected patients to have their own designated bathroom, if possible.
While not specifically looking at the coronavirus, scientists from the City University of Hong Kong found a flushed toilet can release up to 80,000 infectious droplets into the air, depending on the flush mechanism.
Lead author Professor Alvin Lai Chi-keung recommended people close their toilet lid before flushing to ward off infections, but stressed this will not give “complete prevention” against the coronavirus.
He warned particles from human waste may “stick” to a closed toilet lid and be released when it is lifted.
Stressing the importance of extractor fans, Professor Chi-keung told the South China Morning Post 87% of airborne pathogens could be removed from a bathroom if a fan was left on for 15 minutes.
Half-flushes, if possible, may also limit the droplets expelled into the air, the City scientists added.
In 2015, a team from the University of Oklahoma in Oklahoma City reviewed the evidence for “toilet plume”.
They called for further research, but concluded: “Contaminated toilets have been clearly shown to produce large droplet and droplet nuclei bioaerosols during flushing.
“Research suggests this toilet plume could play an important role in the transmission of infectious diseases for which the pathogen is shed in faeces”.
A team from Heriot-Watt University in Edinburgh have put together tips to help keep plumbing systems virus-free, like not ignoring foul smells and running taps for up to 10 seconds at least twice a day.
What is the coronavirus?
The coronavirus tends to cause flu-like symptoms, including fever, cough and slight breathlessness.
As well as coughs, sneezes and faeces, there is also evidence it can survive on surfaces.
In severe cases, pneumonia can come about if the infection spreads to the air sacs in the lungs.
This causes them to become inflamed and filled with fluid or pus.
The lungs then struggle to draw in air, resulting in reduced oxygen in the bloodstream and a build-up of carbon dioxide.
The coronavirus has no “set” treatment, with most patients naturally fighting off the infection.
Those requiring hospitalisation are offered “supportive care”, like ventilation, while their immune system gets to work.