Health officials have issued a warning over a new strain of super gonorrhoea that is resistant to two crucial antibiotics - including a last-ditch resort.
In the first recorded case worldwide, an unidentified English man - who was having regular sex with a woman in the UK - caught the STI from another woman during his travels to south east Asia earlier this year.
Public Health England revealed his gonorrhoea was resistant to ceftriaxone and azithromycin - the two drugs that the World Health Organization recommends to be given to patients with the STI.
The Government-run agency has issued an alert regarding the possible spread of the bug - which proved resistant to recommended treatment.
A PHE report read: "This is the first global report of high-level azithromycin resistant N. gonorrhoeae which is also resistant to ceftriaxone."
It added that it has now "formed an incident management team" to co-ordinate the investigation and contain the spread of the superbug, the Daily Mail reported.
The new case, revealed yesterday, follows repeated warnings over the dangers of super gonorrhoea by concerned health chiefs.
WHO raised concerns two years ago that the STI, once known as the "clap", could become immune to antibiotics in a "matter of years".
The new document stated the man - whose location has also been withheld - attended sexual health services earlier this year.
He was having regular sex with a female in the UK, but also had a one-off encounter with another woman in south-east Asia.
The man told doctors his gonorrhoea symptoms began a month after having sex with the woman on his travels, PHE officials said.
The document does not state whether the Asian woman already had the multi-drug resistant strain of gonorrhoea, or if it mutated.
He was started on a course of ceftriaxone and spectinomycin - but tests showed the STI remained in his throat, suggesting one failed to work.
Laboratory tests revealed a high resistance to azithromycin and ceftriaxone. It also showed the bug was only susceptible to spectinomycin.
The patient - who will be retested in the middle of next month to see if he still has gonorrhoea - is now being treated with daily injections of ertapenem, another antibiotic.
Preliminary STI results for his sexual partner in the UK returned negative for gonorrhoea. She is being followed up.
More than 35,000 people a year are infected with gonorrhoea in England, including record numbers of baby boomers. Only chlamydia and genital warts are more prevalent. Figures show 78 million people worldwide contract gonorrhoea each year.
But a 'super' version of the STI, which is caused by the Neisseria gonorrhoeae bacterium, swept across Britain two years ago, striking London, the South East and the Midlands.
It was resistant to the common antibiotic ciprofloxacin and extended-spectrum cephalosporins, which are the drugs of last resort.
A WHO analysis of STI data around the world previously revealed 97 per cent of countries have reported strains of gonorrhoea that are resistant to ciprofloxacin.
A further 81 per cent stated there was increasing resistance to just azithromycin. And more than 50 countries warned strains were showing some form of resistance to ceftraixone - another last-resort treatment.
Chief Medical Officer Dame Sally Davies has previously written to GPs warning that gonorrhoea could become an 'untreatable disease'.
Super gonorrhoea is one of many antibiotic-resistant infections which together kill an estimated 700,000 people worldwide each year.
Deemed to be one of the biggest threats to humanity, the issue has previously been cited as severe as terrorism and global warming.
Antibiotics have been so overused by GPs and hospital staff for decades that the bacteria have evolved to become resistant.
Doctors claim medicines including penicillin no longer work on sore throats, skin infections and, more seriously, pneumonia.
Dr Gwenda Hughes, head of STIs at PHE, said: 'We are investigating a case who has gonorrhoea which was acquired abroad and is very resistant to the recommended first line treatment.
"First line treatment for gonorrhoea is a combination of two antibiotics (azithromycin and ceftriaxone). This is the first time a case has displayed such high-level resistance to both of these drugs and to most other commonly used antibiotics.
"We are following up this case to ensure that the infection was effectively treated with other options and the risk of any onward transmission is minimised."
More than 35,000 people a year are infected with gonorrhoea in England, including record numbers of baby boomers. Only chlamydia and genital warts are more prevalent.
Figures show 78 million people worldwide contract gonorrhoea, which can often go symptomless for weeks, each year.
Symptoms usually strike within two weeks of infection - but can stay hidden for many months.
In women, symptoms of gonorrhoea can include:
An unusual vaginal discharge, which may be thin or watery and green or yellow in colour Pain or a burning sensation when passing urine Pain or tenderness in the lower abdominal area (this is less common) Bleeding between periods, heavier periods and bleeding after sex (this is less common) In men, symptoms of gonorrhoea can include:
An unusual discharge from the tip of the penis, which may be white, yellow or green Pain or a burning sensation when urinating Inflammation (swelling) of the foreskin Pain or tenderness in the testicles (this is rare)