The toilet seat had the most contamination, while walls had little.
Contrary to previous study findings, closing the toilet lid before flushing doesn't stop aerosolized viruses from contaminating bathroom surfaces, scientists from the University of Arizona and Reckitt Benckiser LLC, the company that makes the disinfectant used in the study, report in the American Journal of Infection Control.
The researchers added a bacteriophage (virus that targets and kills bacteria) to household and public toilet bowls as a proxy for human intestinal viruses. After they flushed the toilets (with the lid open or closed in case of the household toilets), they measured viral contamination of the toilet and bathroom floor and walls.
"Research has demonstrated that people with COVID-19, even those who are asymptomatic, excrete severe acute respiratory syndrome coronavirus (SARS-CoV-2) in fecal matter and other excretions," the researchers wrote. "Viruses contaminating urine and feces can be aerosolized in building restrooms during toilet flushing."
The resulting toilet aerosol plumes, they said, can land on surfaces more than 5 feet away.
Funded and authored by the company wanting to sell you their disinfectant.
Conflicts of interest: Drs. Julie McKinney and M. Khalid Ijaz are engaged in R&D at Reckitt Benckiser LLC. The other authors declare no competing interests.
Funding/support: This study was funded by a grant to the University of Arizona from Reckitt Benckiser.
Mythbusters proved that there are fecal bacteria everywhere and as such you can never reasonably completely avoid it. However, they didn't prove whether there are other bacteria or viruses that are kept contained with a closed lid compared to with an open lid, or if the viral/bacterial load is lower with a closed lid.
The only way to stop this would be to change toilet lids to be an air tight seal (with some kind of 1 way valve to allow air in for flushing) or control the air flow, in a way that's strong enough to capture ejected particles, and suck it through a filter.
The second option would have the added benefit of capturing particulates when people are actually farting and shitting, as well as removing the smell.