What are the main STIs?

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The ten most common STIs in the UK are: anogenital warts, chlamydia, genital herpes, gonorrhoea, HIV, hepatitis B, hepatitis C, public lice, syphilis and trichomonas. These are briefly described below.

Anogenital warts are small lumps that develop on the genitals and/or around the anus (back passage). They are sometimes just called genital warts. They are caused by a virus called the human papillomavirus (HPV). However, most people infected with HPV do not develop visible warts. You can be a 'carrier' of the virus without realising it, and you may pass on the virus to others who then develop warts. Treatment options include applying chemicals to the warts or freezing the warts to destroy them.

Chlamydia is caused by a bacterium (germ) called Chlamydia trachomatis. It is the most common STI in the UK. Symptoms include a vaginal discharge in women, and a discharge from the penis in men. You can be infected with chlamydia for months, even years, without realising it as it often causes no symptoms. However, even if you have no symptoms, you can still pass on the infection and complications may develop if it is left untreated (such as pelvic infection and infertility in women). A short course of an antibiotic clears chlamydia in most cases.

Genital herpes is caused by the herpes simplex virus. Once you catch this virus it stays with you for life but lies dormant without causing symptoms for most of the time. In fact, many people who are infected with this virus never have symptoms. If symptoms occur, they can range from a mild soreness to many painful blisters on the vulva or penis and surrounding area. A first episode of symptoms can last 2-3 weeks, but may be shorter. Recurrent episodes of symptoms then develop in some cases from time to time, but are usually less severe than the first episode. (It is similar to having 'cold sores' on the genitals from time to time.) Antiviral medication can ease symptoms when they develop.

Gonorrhoea is caused by a bacterium called Neisseria gonorrhoeae. Symptoms include a vaginal discharge in women, and a discharge from the penis in men. Again, some people infected with gonorrhoea do not develop symptoms. However, even if you have no symptoms, you can still pass on the infection and complications may develop if it is left untreated (such as pelvic infection and infertility in women). A short course of an antibiotic clears gonorrhoea in most cases.