Research: Sexually transmitted infections: South East data

This report presents data on sexually transmitted infection (STI) diagnoses among South East residents. It includes new data from 2025, with historical trends going back to 2016. Any data from 2020 and 2021 should be interpreted with caution, because the COVID-19 pandemic affected both sexual behaviour and STI testing rates.

Of all the UK Health Security Agency (UKHSA)’s regions, the South East has the third lowest rate of new STI diagnoses in England. However, STIs remain an important public health issue in the South East.

In 2025, 38,320 new STIs were diagnosed in the South East, a rate of 410 diagnoses per 100,000. Rates across upper tier local authorities ranged from 240 per 100,000 on the Isle of Wight to 1,001 per 100,000 in Brighton and Hove.

The number of STI diagnoses in the South East decreased (-6%) between 2024 and 2025. Decreases were seen in 4 of the 5 main STIs: syphilis (-11%), gonorrhoea (-4%), chlamydia (-9%), and genital warts (-9%). Genital herpes diagnoses increased by +5%.

UKHSA recommends that local areas should be working towards a chlamydia detection rate of at least 3,250 per 100,000 women and girls aged 15 to 24 years, as a measure of screening effectiveness. This detection rate is an indicator in the Public Health Outcomes Framework. The South East did not achieve this target in 2025, with 1,082 detections per 100,000 (down from 1,287 per 100,000 in 2024).

Rates of STI diagnoses differ between men and women (435 and 356 per 100,000, respectively). Gay and bisexual men are one of the groups disproportionately impacted by STIs. Where gender and sexual orientation were known, 19% of the South East STI diagnoses in 2025 were among gay and bisexual men. The proportions were higher for syphilis (66%) and gonorrhoea (57%).