To Contain Viral Spread, Should We Close The Toilet Lid Or Leave It Up? Nope, You’re Wrong

Nobody likes being sprayed with toilet juice (we assume) – and yet every time we flush away our waste, those miracles of modern engineering suddenly turn into raging sewage volcanoes. “No problem,” you might think, “my toilet comes with a fancy-pants lid, I can just close it!” Well, boy do we have bad news for you.

“Closing toilet lids has no meaningful impact on preventing the spread of viral particles,” said Charles Gerba, professor of virology at the University of Arizona and senior author of a recent study that measured the spread of viral particles by flushing a toilet.

“Our study highlights the importance of regular disinfection of toilets to reduce contamination and prevent the spread of viruses,” he said in a statement on the findings.

That isn’t to say that closing your toilet lid while it flushes is a bad idea: multiple studies have shown that it’s good for containing the spread of bacterial pathogens, which tend to be bigger than their viral equivalents. Plus, you know, less poop and pee in the air is definitely a benefit.

But when Gerba and colleagues seeded both public and home toilets with doses of a virus – the MS2 bacteriophage, a type of virus that infects bacteria, which is not dangerous to humans but acted as a proxy for all those other nasties that are – and gave them a flush, they found having the lid up or down gave no statistically significant difference in the amount of virus that ended up around the bathroom.

“Our study demonstrated that lid position (up or down) prior to flushing of household or public toilets of United States design seeded with MS2 bacteriophage had no significant effect on the MS2 cross contamination of household restroom surfaces,” notes the study. “MS2 was recovered from all restroom surfaces tested, and lid closure had no impact on the results.”

What closing the lid did do, however, was to slightly redirect the spew. If you want, for some reason, to protect the bits of floor to the left and right in front of your toilet from getting quite so mucky, then don’t close the lid; if keeping the wall to the left clean is your priority, then shut it before you flush it.

If you were eating while reading this then… sorry I guess? A schematic depiction of MS2 aerosolization and spread to adjacent areas after flushing a home toilet of U.S design
Image Credit: Gerber et al., 2024, (CC BY 4.0)

Or wait, no, that’s bad advice. If you want to keep any area of your bathroom clean, then there’s actually something much better than just flushing and hoping for the best: disinfect it. Along with the bad news about pathogen spread, the study also had a silver lining – a review of the effectiveness of cleaning the toilet.

“Cleaning of the toilet bowl with a disinfectant (formulated hydrochloric acid) and bowl brush in this study significantly […] reduced MS2 contamination of toilet bowl water, with >4 log10 (>99.99 percent) reduction, compared to cleaning with a brush only,” the study confirms. “In addition, it was found that the toilet bowl brush itself was significantly […] less contaminated when a disinfectant product was used during cleaning. In this case, a 1.6 log10 (97.64 percent) reduction was observed.”

In other words: if you don’t want to get sick – and frankly, we’re gonna just assume you don’t – clean your dang bathroom more often. 

The study is published in the American Journal of Infection Control.

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