One reason STIs spread is because people think they can only be infected if they have sexual intercourse. That’s wrong. Some STIs, like herpes or genital warts, can spread through skin-to-skin contact with an infected area.
Another myth about STIs is that you can’t get them if you have oral or anal sex. That’s also wrong, because the viruses or bacteria that cause STIs can enter the body through tiny cuts or tears in the mouth and anus, as well as the genitals.
STIs spread easily because it is difficult to tell if someone has an STI. Many people with STIs don’t know that they have them. These people are at risk of passing an STI on to their sex partners without realising it.