I'm a teacher and have had red eared sliders living in a tank in my room. Students have held them and I've never had an issue. Same with my 3-toed box turtle. As long as you provide a relatively clean environment to minimize bacteria growth and wash hands (and lips apparently) after handling them there shouldn't be a problem.
You should never do that! Salmonella is dangerous! I had to go to the ER once because I was be an idiot about it once. This is not a lie. If salmonella gets into your body, it can really mess you up. It doesn’t affect you right away, but after a day or two you will feel very, very sick.