Research shows aerosols from toilets can be source of SARS-CoV-2 spread; close lid before flushing to prevent COVID-19 transmission

It is an established fact that COVID-19 infection spreads through the aerosols generated by the cough and sneeze of an infected person. Several measures have been implemented, including the mandatory wearing of masks and social distancing, in order to prevent the virus from spreading. However, some studies have shown that wastewater can also be one of the modes of transmission of SARS-CoV-2 virus in a community where the source of infection is unknown.

Moreover, in a recent article published in the journal Physics of Fluids on 16 June 2020, it was found that flushing a toilet can generate a cloud of aerosol droplets which can stay airborne for a long period of time and thus, can be inhaled by the next user.

Toilet flush can produce viral aerosols 

The study conducted by the researchers of the People’s Republic of China concluded that due to the strong turbulence of single-inlet flushing and annular flushing, there is a generation of aerosols in the toilet with an upward speed of 5 metres per second. This allows these aerosols to expel out of the toilet bowl.

The study stated that around 40-60 percent of the particles can rise above the toilet seat to a height of 106.5 cms from the ground. They further stated that even 35 to 70 seconds after flushing, the diffused particles can still climb up the toilet bowl at a height of 0.27 to 0.37 cms per second.

In conclusion, the scientists stated that in order to stay safe, people should close the toilet lid before flushing, clean the toilet surface before using it, as the viral droplets could be present on the toilet surface, and wash their hands thoroughly after using the toilet.

Presence of SARS-CoV-2 virus in wastewater systems

According to a Japanese study done by the Toyama Prefectural University, Kanazawa University and Kyoto University, there has been a confirmed presence of the SARS-CoV-2 virus in the wastewater plants of four treatment plants in Ishikawa and Toyama prefectures in western Japan. In this study, the researchers studied 27 samples of wastewater out of which seven samples tested positive for SARS-CoV-2 virus in them. The researchers stated that wastewater testing could be helpful in estimating the number of infected people in a region without testing every individual.

Testing the wastewater system to find the infection

In order to test any abnormality in the wastewater systems, a technique called the wastewater-based epidemiology (WBE) is used, in which the scientists can find the contaminants and pathogens in a human by testing the faeces and urine from their wastewater systems. This technique has been used in the past for various diseases such as malaria, rotavirus A, Zika virus and even HIV.

The testing is done with the help of a simple testing paper device (preloaded with biochemical reagents) which is folded and unfolded in steps. This helps in filtering the DNA or RNA of the pathogens that were derived from the wastewater samples.

The results can be seen instantly; a green circle on the paper indicates positive pathogens whereas a blue circle indicates negative.

For more information, read our article on Wastewater test for early detection of COVID-19 .

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