Infectious Disease

Viruses still ‘ejected’ from toilets even when lid is closed

Evan Vega January 27, 2024

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January 26, 2024

2 min read

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Key takeaways:

Toilet lid position before flushing has no significant impact on bathroom surface contamination with viruses.
Use of a disinfectant helped limit the amount of virus in toilet bowl water.

Closing the toilet lid before flushing does not lessen the risk of contaminating bathroom surfaces with viruses, researchers found.

Past studies have shown that closing a toilet lid before flushing can limit the spread of bacteria.

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Simulated viruses were still ejected from a toilet with the lid down. Image: Adobe Stock

“We wanted to determine if closing the toilet lid as recommended by some would reduce the amount of viruses ejected from the toilet after flushing,” Charles P. Gerba, PhD, a professor of virology at the University of Arizona, told Healio. “Also, the toilet seat gets more contaminated because the air from the toilet bowl is forced over the toilet seat — something we wanted to assess.”

For their study, Gerba and colleagues added bacteriophage MS2 — a surrogate for intestinal viruses — to toilet bowls and flushed, then tested the toilet and other surrounding surfaces for viral contamination.

Overall, the study demonstrated that even with the toilet lid closed, viruses were still “ejected” from the toilet after flushing, Gerba said.

Specifically, Gerba and colleagues found that contamination of the toilet seat or restroom surfaces was not statistically different after flushing, regardless of the toilet lid’s position. When the toilet lid was closed, however, contamination of the toilet seat bottom in toilets receiving high-dose bacteriophage was 99.9% higher than in toilets receiving low-dose phage.

In terms of other surfaces, wall contamination was minimal regardless of lid position and there was no significant difference in contamination level between any surfaces, according to the researchers. Floor contamination was not reduced by consistently closing the lid before flushing.

The researchers also assessed phage contamination during the cleaning of household toilets with a toilet brush both before and after the use of a disinfectant product. Overall, the results indicated similar patterns of surface contamination before or after the cleaning product was used: toilet lid contamination was minimal in both conditions, the toilet seat was highly contaminated with phage and relatively high levels of viral contamination were found on the toilet brush, brush caddy and toilet bowl rim after cleaning the toilet bowl with a brush and disinfectant.

The study did demonstrate a greater than 99.99% reduction in contamination of the toilet bowl water after cleaning with a disinfectant vs. no product, whereas brush contamination was reduced by 97.64% when the product was used vs. no product.

Gerba explained that the cleaning that reduced the amount of virus would also be effective at reducing bacteria, especially considering that bacteria “are less resistant to disinfectants than viruses.”

Gerba said the results provide an important message to infection prevention and control staff.

“Be sure not to flush infected bodily fluids down the toilet, and if someone is infected with an enteric infection, be sure to disinfect surfaces in/on the toilet with a disinfectant spray or disinfecting wipes.”

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