Helsinki sees drop in chlamydia but rise in gonorrhoea cases

Chlamydia infections in Finland have fallen by 20% since 2024, according to the Finnish Institute for Health and Welfare (THL), though the reason remains unclear.

At the same time, gonorrhoea cases have doubled year-on-year since the pandemic, particularly among young adults—the same group most affected by chlamydia. In 2025, Finland recorded around 2,000 gonorrhoea infections, nearly half of them in Helsinki alone.

Eija Hiltunen-Back, a specialist in skin and sexually transmitted diseases at Helsinki University Hospital (HUS), noted that while chlamydia remains the most common STI in Finland, with roughly 12,000 cases nationwide last year, its decline is puzzling. A similar trend is observed across Europe, with no clear explanation.

Gonorrhoea, traditionally more common in men, is now increasingly detected in young women, often with mild or no symptoms. This delays diagnosis and treatment, raising the risk of long-term complications such as infertility.

Preliminary data for early 2026 suggests the rapid rise in gonorrhoea cases may be slowing, though Hiltunen-Back cautioned that testing typically increases after the summer, which could reveal higher numbers.