Image caption Infection is caused by the bacterium Neisseria gonorrhoea

Health experts in England and Wales are on high alert for "untreatable" gonorrhoea that, in some countries, has developed resistance to antibiotics.

Although most UK cases are readily treatable, infection rates are rising.

And the Health Protection Agency (HPA) is launching an action plan to reduce transmission and monitor for and rapidly detect drug resistance.

Gonorrhoea is the second most common bacterial sexually transmitted infection (STI) in England.

Gonorrhoea Infection can be passed on by unprotected vaginal, oral or anal sex

It can also be passed from a pregnant woman to her baby

Of those infected, about one in 10 men and nearly half of women do not have symptoms

Gonorrhoea can be easily diagnosed with a swab test

In 2011, newly diagnosed cases jumped 25% to nearly 21,000.

At the same time, the risk of gonorrhoea developing resistance to the antibiotics doctors normally prescribe - ceftriaxone and azithromycin - fell slightly for the first time in five years.

However, cases of treatment failure have now been reported globally and, with no new drugs in the pipeline, England's chief medical officer has advised the government to add the threat of the infection's resistance to front-line antibiotics to the civil emergencies risk register.

Dame Sally Davies said: "We have seen a worrying rise in cases of drug-resistant gonorrhoea over the last decade.

"Antimicrobial resistance to common drugs will increasingly threaten our ability to tackle infections, and the Health Protection Agency's work is vital to addressing this threat."

Dr Gwenda Hughes, head of STI surveillance at the HPA, said: "We are seriously concerned about continuing high levels of gonorrhoea transmission and repeat infection, suggesting we need to do more to reduce unsafe sexual behaviour."

She said a priority was to encourage safer sexual behaviour and condom use, particularly among high-risk groups such as men who have sex with men, who account for more than a third of new gonorrhoea cases.

The first case of antibiotic-resistant gonorrhoea was found in Japan in 2011. Sweden has also encountered a case.