What are STIs?

STIs are sexually transmitted infections. They are sometimes referred to as sexually transmitted diseases or STDs. This means they are most often - but not exclusively - spread by sexual intercourse. HIV, chlamydia, genital herpes, genital warts, gonorrhoea, syphilis, trichomoniasis and some forms of hepatitis are all STIs.

STIs used to be called venereal diseases or VD. They are among the most common contagious diseases.