Oral sex is causing the spread of a dangerous gonorrhoea superbug, experts have warned.

The untreatable strain of gonorrhoea is rapidly spreading across the world putting millions of lives at risk, the World Health Organisation has warned.

Experts said that incurable gonorrhoea has started to spread after becoming resistant to antibiotics, which has been partly caused by oral sex and a decline in condom use.

The sexually transmitted bacteria can live at the back of the throat and, because of this, has been evolve immunity to antibiotics used to treat common throat infections.

The WHO issued a warning after it confirmed that three people had contracted the superbug.

Oral sex is causing the spread of an untreatable gonorrhoea superbug, experts have warned

The rise of 'super gonorrhoea'

The bacterial infection is normally treated with a short and simple dose of antibiotics.

But gonorrhoea has become increasingly resistant to common antibiotics.

Bacteria become immune to antibiotics when they evolve new self defense mechanisms to stop the drugs from being effective.

Antibiotic resistance is chiefly driven by the over-subscription of antibiotics, according to researchers.

In 2016, experts from the WHO warned that a 'super' strain of gonorrhoea could become immune to antibiotics in a 'matter of years'.

But now experts from the WHO have said it is 'only a matter of time' before last-resort gonorrhoea antibiotics would be of no use at all.

Experts said that incurable gonorrhoea has started to spread after becoming resistant to antibiotics, which has been partly caused by oral sex and a decline in condom use

'Gonorrhoea is a very smart bug,' said Teodora Wi, a human reproduction specialist at the Geneva-based UN health agency.

'Every time you introduce a new type of antibiotic to treat it, this bug develops resistance to it.'

Role of oral sex in spreading the disease

She added that the rapid spread of the antibiotic resistant bacteria has been caused in part by oral sex.

The sexually transmitted bacteria can live at the back of the throat and, because of this, is frequently exposed to antibiotics used to treat throat infections.

Repeated exposure to antibiotics makes it easier for bacteria to evolve drug resistance.

'When you use antibiotics to treat infections like a normal sore throat, this mixes with the Neisseria species [gonorrhoea bacteria] in your throat and this results in resistance,' Dr Wi told the BBC.

A decline in condom use, caused by misguided fears that they cause HIV in the developing world, use is also thought to have helped the infection to spread, she added.

Condoms protect against the spread of the disease, which is transferred through sexual fluids.

Dr Wi said medics have now documented three specific cases - one each in Japan, France and Spain - of patients with strains of gonorrhoea against which no known antibiotic is effective.

'These are cases that can infect others. It can be transmitted,' she said.

'And these cases may just be the tip of the iceberg, since systems to diagnose and report untreatable infections are lacking in lower-income countries where gonorrhoea is actually more common.'

'Pressing need' for new medicines

The WHO found the disease has evolved widespread resistance to a first-line antibiotic known as medicine ciprofloxacin, and is currently becoming increasingly resistant to azithromycin.

In most countries, last-case antibiotics are now the only single antibiotics that remain effective for treating gonorrhoea, according to researchers.

Manica Balasegaram, director of the Global Antibiotic Research and Development Partnership, said the situation was 'grim' and there was a 'pressing need' for new medicines.

The pipeline is very thin, with only three potential new gonorrhoea drugs in development and no guarantee any will prove effective in final-stage trials, he said.

'We urgently need to seize the opportunities we have with existing drugs and candidates in the pipeline,' he said.

'Any new treatment developed should be accessible to everyone who needs it, while ensuring it is used appropriately, so that drug resistance is slowed as much as possible.'