Bacteria and viruses must exit one host and enter your body by a port of entry (POE) to make you sick.
POEs include the mouth (entrance into your lungs and gut), nose, eyes, the skin (through insect bites, cuts and scrapes leading to your bloodstream), urogenital tract (the penis and vagina) and, in very few cases, the anus. However, the anus is mostly a place for bacteria to exit, which is where something called “enterics” comes into play.
If someone is hosting enteric bacterial colony (one that lives in the guts and exits through feces), dropping a deuce can allow it to escape into the toilet water, thus contaminating the toilet bowl. The potential for infection does not lie in the sit-and-splash scenario. Rather, the infection can occur once the contaminated toilet is flushed and little bits of water are aerosolized — simply put, microscopic bits are splashed up and carried through the air.
According to a 2005 article published in “The Journal of Applied Microbiology,” two researchers discovered that once a colony of bacteria has been shed into the toilet, it stays inside the bowl and in the water long after the first flush. Each flush following the initial poop forms contaminated aerosols in the air surrounding the toilet. There is no way a flimsy cover localized to the toilet seat can protect someone from these various forms of contamination.
Sorry for upping your anxiety.
The exit in this case is the anus, via poop, and the POE is the mouth — OK, I just threw up a little while writing that. So yes, this is something to worry about. The toilet seat liners can’t protect you from anything other than your own paranoia. And after reading this article, nothing can protect you from paranoia.
The best you can do is wash your hands thoroughly and avoid putting them in your mouth. And don’t hang out in the bathroom stall after you’ve flushed the toilet. And don’t sit on the pot and text, because the glassy surface of your phone screen is a great place for microbes to sit and wait. Then, when you put the phone to your face later in the day to call your honey boo-boo, BAM — gut bacteria gets on your face!
Now, if you’re sitting there thinking, “Wait, but she didn’t say if the toilet seat itself is crawling with STDs or pubic lice or anything!” here’s the answer for you.
You can’t get infections from the toilet seat itself. The only possible way I could see that occurring is if your rear end was scraped up and bloody, allowing for the POE (bloodstream) to be exposed. But, that would require the previous seat-sitter to have shed bloodborne pathogens and left the bloody spots on the seat. This situation is both severely unlikely and very disgusting.
Regular hygiene practices and hand sanitizer go a long way towards preventing any kind of sickness. The Mayo Clinic says to wash your hands with soap and warm water, scrubbing all surfaces of the hands for 20 seconds. Under the nails and between the fingers are often places where bacteria love to hide, so be thorough with scrubbing to stay safe!