Gonorrhoea is becoming increasingly resistant to antibiotics, and could be untreatable in the future, health officials have warned as a report reveals a rise in super-strength cases in England.

There were 85,000 cases of gonorrhoea diagnosed in England last year, the highest level since records began in 1918. Left untreated, it can lead to serious health problems including pelvic inflammatory disease and infertility.

The vast majority of cases can be treated. But recently there has been an increase in people diagnosed with strands that are resistant to ceftriaxone, the “first line” antibiotic typically used to treat the infection.

Most of those affected were in their 20s, heterosexual, and acquired the infection abroad, though some had no travel history, according to the UK Health Security Agency (UKHSA). The public health agency confirmed there had been transmission of ceftriaxone-resistant gonorrhoea in England.