June 6, 2012 -- Gonorrhea is fast becoming untreatable, spurring an urgent call to action by the World Health Organization (WHO).

The WHO alert follows an even more strident warning by CDC researcher Gail A. Bolan, MD, and colleagues.

"It is time to sound the alarm," Bolan and colleagues wrote last February in the New England Journal of Medicine. Resistance to all known antibiotics, they warn, is "threatening our ability to cure gonorrhea."

Gonorrhea, sometimes called the clap, is a sexually transmitted disease. With more than 600,000 new cases a year in the U.S., it trails only chlamydia as the nation's most common STD.

Gonorrhea bacteria, Neisseria gonorrhoeae, have a long history of evading treatment:

In the 1940s, gonorrhea became resistant to sulfanilamide.

In the 1980s, gonorrhea became resistant to penicillin, tetracycline, chloramphenicol, erythromycin, and streptomycin.

By 2007, gonorrhea became resistant to fluoroquinolones, including ciprofloxacin.

When the dust cleared, there was only one line of defense against gonorrhea: third-generation cephalosporin antibiotics. The currently recommended cephalosporins are injectable ceftriaxone (preferred) and oral cefixime.