Fortunately, the answer is no. Venereal diseases like syphilis and gonorrhea are only transmitted through person-to-person contact. However, studies have shown that hard surfaces like toilet seats can hold bacteria or viruses for a while, including the norovirus, E. coli, streptococcus and others. So it does make sense to carry antiseptic wipes to clean public toilet seats before you use them. Careful handwashing any time you use a restroom is probably the most important way to ward off germs. So be vigilant, but try not to get too worried about using a public restroom!