Closing the lid on the toilet seat before flushing does not prevent the spread of germs. The water jet projects pathogen-carrying particles all around the bowl.
American researchers visualized, using green lasers, the propagation of droplets emitted by a toilet flush. Adding disinfectant to the toilet bowl before flushes or using disinfectant dispensers in the toilet tank were two effective ways to reduce contamination from flushing the toilet. But as Gabriel Birgand reminds us, “the use of biocidal products must be done sparingly”