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Home Topics Infectious Diseases Infections A-Z STIs (Sexually Transmitted Infections)

STIs (Sexually Transmitted Infections)


Sexually transmitted infections (STIs) are diseases that can be transmitted by unprotected sex.


Not everyone with an STI will have signs and symptoms of the condition. If a person does present with symptoms, these may include increased discharge, pain or ulcers. If the STIs are left undetected and untreated they may result in serious complications in later years. The role of the HPA is to contribute to protecting the population from infection through routine surveillance, modelling, epidemiological investigation and research.

  Disease statistics and surveillance
STI Annual Data Tables

STI Annual Data Tables

STI data tables and slide sets are updated on an annual basis. They show information on the five main STIs and other STIs in the UK, by sex, age-group, and geographical distribution.

More information on STI Annual Data Tables


Genital Chlamydia trachomatis is the most commonly diagnosed STI in the United Kingdom. Highest rates are seen in mainly young people aged under 25 years.

More information on Chlamydia

electron micrograph (TEM) image of numerous herpes simplex virions

Genital Herpes

Genital herpes simplex virus (HSV) infection is the most common ulcerative sexually transmitted disease in the UK. Symptoms can start with mild soreness and groups of small painful blisters appearing on the genitals and surrounding areas. Further episodes of these symptoms can occur from time to time as recurrent episodes.

More Information on Genital Herpes

teenage girl HPV

HPV - Genital Warts

There are many (over 100) types of Human papillomavirus (HPV), around 40 of which are sexually acquired and can infect the genital tract. Certain genital HPV infections can cause cervical cancer, other cancers and genital warts.

More Information on HPV

Gonorrhoea cells, courtesy CDC library


Neisseria gonorrhoeae is the second most common bacterial STI in the United Kingdom. Young people are most commonly infected, with current rates highest in males aged 20-24 years and females aged 16-19 years.

More information on Gonorrhoea

Blood sample


Syphilis is caused by a bacterial spirochete Treponema pallidum subspecies pallidum. Syphilis can be transmitted between partners during sexual intercourse and from an infected pregnant woman across the placenta to a developing baby.

More information on Syphilis

Male torso

Lymphogranuloma venereum (LGV)

Lymphogranuloma venereum (LGV) is a sexually transmitted disease caused by a specific type of Chlamydia trachomatis (serovars L1, L2, and L3). LGV is highly prevalent in parts of Africa, Asia, and South America but has been rare in Western Europe for many decades.

More information on LGV