New alert on bacteria expelled by flushing toilets

A Korean team tested and measured a kind of “permanent” contamination in toilets, due to contaminated microdroplets projected into the air by flushing.

By the end of this column, you may never flush the toilet like you used to. Géraldine Zamansky, journalist for the Health Magazine on France 5, reveals to us the results, in preview, of a Korean presentation at a major international congress of infectious diseases.

franceinfo: Was this infectious diseases conference devoted to toilets?

Geraldine Zamansky: It is very serious. This Korean study provides additional proof of the risks of spreading infections when flushing the toilet without closing the toilet lid.

It all started with the design of a device that only allows this action after closing, as Jihye Park of the Asan Medical Center in Seoul explained to me. He will present his results at the ESCMID Global International Congress at the end of the month. With this system, only six colonies of bacteria were collected around the throne, in the equipped bathrooms, compared to 14 colonies, in the others.

So closing the toilet lid before flushing reduces contamination, but doesn’t eliminate it completely?

Yes, and yet, this Korean team makes it clear that no one had just used the toilet before their test. They therefore measured a sort of “permanent” contamination. This type of persistence is also at the origin of recent French research in this area.

Dr Jeanne Couturier-Dagher, environmental microbiologist at Saint-Antoine Hospital in Paris, told me how in 2016, two cases of Legionnaires’ disease – fortunately cured – had been identified, in the same room, at 6 months of difference.

Genetic analysis of the bacteria taken from the toilet showed that they were identical to those contained in the patient’s lungs. This was the first such irrefutable proof of such transmission.

That is to say, do the droplets from the flush go to the lungs?

Yes, we breathe contaminated microdroplets, projected into the air by the flush. And the “investigators” from Saint-Antoine were then confronted with another family of bacteria which survive, once they have fallen around the toilet, on the nearby sink faucet or the door handle for example.

The hands then take over, via the food, to lead the enemy to the digestive tract. In 2018, the culprit bacteria were found at the water inlet point, full of scale, under the porcelain rim of the toilet. Impossible to clean, they have all been changed in the affected department. Then, Dr Couturier-Dagher told me how they had experimentally confirmed the different contaminations in 2022… Scary.

So, a suggestion for use, especially in public toilets: close the bowl before flushing, try to block your breathing a little. And in the case of a classic faucet, use a hand towel to close it after washing, and touch the door when leaving. Because everything may have been contaminated. Otherwise, there is also hydroalcoholic gel…