A new study published in the journal Physics of Fluids says that blocking the path of faecal-oral transmission, which commonly occurs during toilet usage, is key to suppressing the spread of the novel coronavirus.
What does the study say?
The study points out that flushing a toilet generates “strong turbulence within the bowl”. The question is if this turbulent flow can expel aerosol particles containing viruses out of the bowl.
The authors say that upward velocity of as much as 5 m/second is produced while flushing, which is capable of expelling aerosol particles out of the toilet bowl. Further, they note that 40-60 per cent of the total number of particles can rise above the toilet seat to cause a large-area spread, with the height of particles reaching more than 106 cm from the ground. Even after flushing (35-70 seconds) after the last flushing, the diffused particles continue to climb.
The study also says that as per the characteristics of faecal-oral transmission, there are likely to be a large amount of viruses within the toilet bowl when an infected person uses it, and therefore, toilets should be regarded as an infection source. Improper toilet use increases the chances that such a transmission will occur.
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“A confirmed case usually remains at home for isolation, where shared use of a bathroom is inevitable. The daily flow of people in a public washroom is stunningly large: thus, a confirmed case may cause a massive number of infections. For these reasons, investigation of toilets in the context of epidemic prevention is imperative,” the study says.
What is faecal-oral transmission and what do we know about it?
It is one of the ways by which a disease can be transmitted from an infectious individual to another. Essentially, this means the transmission of disease through the ingestion of contaminated feed or water (contaminated by faeces, urine etc.).
In the case of SARS-CoV-2, while the presence of the virus has been found in faeces, it cannot be said with certainty if the virus can be transmitted through faeces. Professor Richard Quilliam of the University of Sterling in the UK said in a statement last month that the virus was found in human faeces up to 33 days after the patient tested negative for the respiratory symptoms of Covid-19. He also pointed out that viral shedding from the digestive system could last longer than shedding from the respiratory tract.
In India, the Ministry of Health notes in its FAQs that spread of the novel coronavirus through the faecal-oral route is not the main feature of the outbreak, and the primary route remains droplets from an infected person when they cough or sneeze.
So why is faecal-oral transmission a cause for concern?
Other coronaviruses such as SARS-CoV and MERS are known to be transmitted through the faecal-oral route. This mode of transmission has also been noticed in common intestinal pathogens, norovirus and rotavirus.
“Therefore, blocking the path of faecal–oral transmission can reduce the probability of cross-infection in surrounding areas, thus suppressing the global spread of emerging and re-emerging viruses,” the authors of the study have said.
What should be done to prevent transmission through this route?
The authors recommend that toilet seats should be put down before flushing and seats should be cleaned before using since floating virus particles can be present on the surface. The authors urge toilet manufacturers to design toilets in which the lid is automatically put down before flushing and cleaned before and after flushing. Alternatively, they mention the new design of waterless toilets that can suppress the transmission of pathogens.
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