Many sexually transmitted infections (STIs) do not cause symptoms and are therefore not recognized by affected individuals as diseases. STIs are spread by the transfer of organisms from person-to-person during sexual contact. In addition to the traditional STIs (syphilis and gonorrhoea), the spectrum of STIs now includes the following: HIV, which causes AIDS; chlamydia trachomatis; human papillomavirus (HPV), which can cause cervical, penile or anal cancer; genital herpes; chancroid; genital mycoplasmas; hepatitis B; trichomoniasis; enteric infections; and ectoparasitic diseases (i.e. diseases caused by organisms that live on the outside of the host’s body). The complexity and scope of STIs have increased dramatically since the 1980s; more than 30 disease-causing organisms and syndromes are now recognized as belonging in this category. (UNAIDS Terminology Guidelines, 2015)