A magnified look at the bacteria that causes gonorrhea: A new drug-resistant mutation of the STD, first spotted in Japan in 2008, has been seen in countries from Australia to England.

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repare to worry about yet another super bug. The World Health Organization is warning governments and doctors to be on the lookout for a drug-resistant strain of gonorrhea, the world's second most common sexually transmitted disease. Are we in the early stage of the next big public health crisis? Here, a brief guide:

What exactly is gonorrhea?
It's a bacterial infection commonly spread through any kind of sexual contact. Untreated, it can cause reactions ranging from painful urination to spontaneous abortion, and increase the risk of contracting HIV. Babies born to infected women have a 50-50 chance of developing eye infections that can leave them blind.

How common is it?
It's the most common sexually transmitted disease after chlamydia. Globally, more than 106 million people are infected each year, including more than 700,000 in the U.S. Exact numbers are hard to pin down, however, as an estimated half of the cases are never reported, according to the Centers for Disease Control and Prevention. Gonorrhea has long been considered "low on the sexual risk register" because, unlike HIV or herpes, doctors have been able to knock it out easily with antibiotics. But that could soon change.

What has changed?
The bacteria mutated to ensure its survival. In 2008, doctors reported finding a strain of gonorrhea in Japan that was resistant to antibiotics. Researchers warned the newly discovered superbug could spread and become a global health threat. Since then, antibiotic-resistant gonorrhea has been diagnosed in several other countries, including Australia, France, Norway, Sweden, and Great Britain. Doctors can usually beat a stubborn case of gonorrhea with a group of antibiotics called cephalosporins, but the superbug can withstand even this last resort treatment. "This organism has basically been developing resistance against every medication we've thrown at it," said Dr. Manjula Lusti-Narasimhan, a WHO scientist.

Can't anything stop it?
WHO has put together a "global action plan" focusing first on shaking doctors and governments out of their complacency. Gonorrhea, known colloquially as the clap, was once "considered the scourge of sailors and soldiers," says Frank Jordans of The Associated Press. Then along came penicillin, and suddenly it was easily treatable, and easily forgotten. To keep the new strain from galloping across the globe, doctors will have to step up efforts to spot gonorrhea. That, along with better sex education and a renewed push to find alternative treatments will be needed to avert a truly dangerous crisis, says Lusti-Narasimhan. "We're not going to be able to get rid of it completely," she says. "But we can limit the spread."

Sources: Associated Press, National Center for Biotechnology Information, TIME