Last August, researchers fretted that gonorrhea, a common STD, had become resistant to all but one class of antibiotic: the cephalosporins. But now, even those don't work for some people anymore.

Incurable gonorrhea has made its way to North America, a new study has found. More than six percent of patients with gonorrhea at a Toronto health clinic were found to have an incurable form of the infection, according to a study published Tuesday in the Journal of the American Medical Association.

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A total of 133 gonorrhea patients at the Toronto clinic were treated with cephalosporins. Out of those, nine still had the disease after getting the drugs, which translates into one in 15 people, the Daily Mail reported. This study marks the first time that cephalosporin-resistant gonorrhea has been found in humans in North America.

"Cephalosporin treatment failures have now been documented in North America," Robert Kirkcaldy of the CDC wrote in an accompanying editorial. "Although this milestone was expected, its arrival is deeply troubling." And lead researcher Vanessa Allen told US News & World report that "basically, the problem appears worse than we originally thought."