A sexually transmitted infection (STI) is an infection that you can get from having sex with a person who is infected. Sex can mean oral sex (mouth on genitals), vaginal sex (penis in vagina) or anal sex (penis in anus). People can have STIs and have no signs or symptoms of disease.
You may get symptoms from an STI or you may not. The only way to be sure is to have an STI test. If your partner tells you he or she has an STI, ask for the name of the disease. Go to your doctor, a sexual health clinic or an STI clinic to get tested and treated.