A highly drug-resistant strain of gonorrhoea has broken out in Leeds, with ten confirmed cases so far.
A further four cases have been reported in Macclesfield, Scunthorpe and Oldham, with all 14 patients being heterosexual.
This new strain of the disease, which was first reported in March, is resistant to azithromycin, an antibiotic used to treat the drug alongside ceftriaxone.
There are likely to be many more undiagnosed cases, prompting the British Association for Sexual Health to raise a nationwide alert.
Speaking to the BBC, Dr Jan Clarke, president of the association, said: “It was sufficiently serious to alert our whole national chain of clinics that there is the possibility that we’ve got a very resistant strain of gonorrhoea.
“We are really skating on thin ice as far as treating gonorrhoea is concerned at the moment.”
Dr Mike Gent from Public Health England said: “We can confirm investigations are under way.
“Those affected are being treated with an alternative antibiotic, but the resistance to first-line treatment remains a concern.
“The bacteria that cause gonorrhoea are known to mutate and develop new resistance, so we cannot afford to be complacent.”
Gonorrhea, the second most common STI, is caused by the bacterium neisseria gonorrhoeae and symptoms include thick coloured discharge, pain when urinating and bleeding between periods.
However, the majority of women and men having sex with men, and one in ten heterosexual men, do not receive any symptoms.
If untreated, the disease can lead to infertility and pelvic inflammatory disease.
Image: Centres for Disease Control and Prevention