Until recently, gonorrhea wasn't exactly headline news. The STD affects 300,000 Americans every year, down from a peak of 1 million in the 1970s, when it was treatable with some half-dozen antibiotics, including Cipro. Today, only one class of drugs can kill gonorrhea – cephalosporins – because the bacteria that cause the STD have become resistant to most antibiotics. For this reason, the number of gonorrhea cases in the U.S. has risen for the first time in decades, while the number of cases worldwide has spiked by more than 70 percent since 1999. "Right now, that's our remaining drug that's reliably effective," says Dr. Robert Kirkcaldy, an epidemiologist at the Centers for Disease Control and Prevention (CDC). "We're facing an emerging public-health threat, and now's the time for people to take this seriously."

Gonorrhea is the second most commonly reported infectious disease in the U.S. after chlamydia, which affected 1.3 million people in 2010. Asia and Africa have the most cases of gonorrhea, but incidence in the U.S. is rising. "The high risk is in gay men and people who travel to Southeast Asia," says Dr. Jonathan Zenilman, chief of Johns Hopkins' infectious-diseases division. "But in a year, it will be more widely disseminated." Gonorrhea, although not fatal, can cause infertility.

Researchers can't explain exactly why gonorrhea is becoming drug-resistant. One factor may be that antibiotics are given out so freely in gonorrhea-prone Asia and Africa that the bacteria have learned to skirt them. And while one would think pharmaceutical companies would be racing to launch new drugs, few are rushing to the lab. "If you're a drug company, where do you think you'd want to put your resources – into a treatment for gonorrhea where you're done after one dose, or a drug someone has to take for the rest of their lives?" asks Dr. Kimberly Workowski, an infectious-disease expert at Emory University.

The problem with gonorrhea goes beyond the STD. Playing like an outtake from 'Contagion,' the treatment-resistant tuberculosis has popped up in South Africa and Russia, while antibiotic-resistant cholera and typhoid are in Southeast Asia and Africa. Here in the U.S., MRSA, a type of staph, no longer responds to antibiotics. "They're resistant to everything we've got," says Dr. Arjun Srinivasan of the CDC. "Patients are being infected, and we have nothing to offer them. For some, the post-antibiotic era is here."

More information: Unless you are celibate or in a monogamous relationship, your best protection against getting gonorrhea – the drug-resistant kind or otherwise – is to wear condoms when having sex, period.