Putting the Lid Down Won't Cut Germ Spread From a Toilet Flush

THURSDAY, Jan. 25, 2024 (HealthDay news) -- It’s been said that closing the toilet lid before flushing can prevent the spread of all germs, by keeping any flush-produced mist in the bowl.

But a new study refutes that, showing that tiny viral particles spread to many restroom surfaces during toilet flushing -- whether the lid is up or down.

The only effective way of reducing the spread of virus was through disinfection of the toilet, toilet water and nearby surfaces, researchers report Jan. 25 in the American Journal of Infection Control.

“With results showing that closing toilet lids has no meaningful impact on preventing the spread of viral particles, our study highlights the importance of regular disinfection of toilets to reduce contamination and prevent the spread of viruses,” said senior researcher Charles Gerba, a professor of virology at the University of Arizona.

Prior research has demonstrated that flushing a toilet creates an aerosol plume that can travel five feet or more, spreading germs to floors, walls, sinks and other surfaces in a bathroom, researchers said in background notes.

Studies have also found that closing the toilet lid can reduce the spread of harmful bacteria in a bathroom.

However, until now no one had studied whether the same held true for viruses, which tend to be much smaller than bacteria, researchers noted.

In this study, they analyzed the spread of viral particles induced by flushing with an open or closed toilet lid.

The team seeded toilets with varying doses of a virus that’s not harmful to humans, and then collected samples from toilet bowl water and various bathroom surfaces. 

Leaving the lid up or down made no difference in the amount of virus collected from bathroom surfaces, the researchers found. The toilet seat was the most contaminated surface.

Researchers also analyzed the effects of cleaning the toilet, both with and without disinfectant.

Cleaning with just a toilet brush left behind substantial viral contamination, but cleaning with a disinfectant and a brush significantly reduced the amount of virus found in the toilet, researchers said.

The disinfectant/brush combo reduced viral contamination on the toilet by nearly 100%, and on the brush by about 98%, results show.

Adding disinfectant to the bowl before flushing or using disinfectant dispensers in the toilet tank both proved effective in reducing contamination from flushing.

“In healthcare settings, any potential means of pathogen transmission must be addressed to keep all of our patients -- including the most vulnerable, such as immunocompromised individuals -- as healthy as possible,” Gerba said.

Closing the toilet lid did alter the direction of the aerosol plume, researchers found. The floor in front of and to the left of the toilet were more contaminated after flushing with a closed lid than with an open lid.

Given all this, regularly disinfecting the toilet could help reduce the spread of an infection to other people in a household where someone’s battling a viral infection, researchers said.

“This study helps establish a clearer understanding of how pathogens spread and the measures we can take to break those chains of transmission,” Tania Bubb, president of the Association for Professionals in Infection Control and Epidemiology, said in an association news release. “It also underscores the importance of regular disinfection of surfaces in healthcare settings for reducing the spread of viral infections.” 

More information

The University of Iowa has more about toilet flushing and virus spread.

SOURCE: Association for Professionals in Infection Control and Epidemiology, news release, Jan. 25, 2024