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.