What causes STIs?
Several different viruses and bacteria can cause STI’s. Human papillomavirus (HPV) infects up to 80% of sexually active people. It can cause warts, but is more often asymptomatic. Some strains can cause cervical cancer in women. Infection is usually self-limiting and eventually cleared by the immune system. There is no routine test available for HPV infection. Herpes simplex virus (HSV) causes genital herpes. It infects about 12% of adults. Most infections are asymptomatic, but transmission to sexual partners can occur in the absence of symptoms. There is no reliable test for asymptomatic HSV infection. Chlamydia is an important cause of female infertility. It may cause urethral irritation and discharge in men, but is commonly asymptomatic, and infects about 2% of the population. Gonorrhoea, syphilis and HIV infection are, these days, uncommon in heterosexual men but, together with HPV, HSV and chlamydia, are very common in epidemic proportions in gay and bisexual men.
