Sure, conventional wisdom says that doctors can easily cure gonorrhea with antibiotics–good news for the 300,000 people a year in the United States who get it, especially women: Although gonorrhea typically clears up on its own eventually, if it goes untreated it can leave us with pelvic inflammatory disease or infertility.

But here's the scary part: We may not be able to treat it anymore. The bacterium that causes gonorrhea, Neisseria gonorrhoeae, is very crafty, says Gail Bolan, M.D., director of the CDC's Division of STD Prevention. It mutates quickly and has grown resistant to every class of antibiotics used to treat it since the meds first became available in the 1940s. In 2007, doctors turned to cephalosporins, their last antibiotic hope.

Soon enough, cases resistant to some cephalosporins started popping up in Europe and Asia, says Manjula Lusti-Narasimhan, M.D., a scientist at WHO headquarters in Geneva. This January, researchers announced in The Journal of the American Medical Association that almost 7 percent of the gonorrhea cases they studied in one Canadian clinic were resistant to cefixime, a widely used cephalosporin.