Officials at the World Health Organization are urging doctors and public health officials to be alert for untreatable strains of gonorrhea that are resistant to antibiotics. “Superbug” strains of gonorrhea have already appeared that are resistant to the last available line of defense—cephalosporin antibiotics. Countries affected include the U.K., Australia, France, Norway, Sweden and Japan.

Gonorrhea is a very adaptable bacterium that can mutate quickly and easily spread its resistance. Unless new drugs are developed that are effective against gonorrhea, ”In a couple of years it will have become resistant to every treatment option we have available now,” Dr. Manjula Lusti-Narasimhan, a WHO scientist, told the Associated Press.

In the U.S., more than 700,000 people are infected with gonorrhea each year, according to the Centers for Disease Control and Prevention. Less than half the cases, however, are reported.

As a sexually transmitted disease, gonorrhea is spread though oral, vaginal, or anal sex. People who have been treated can become infected again through sexual contact with someone who is infected.

In men, symptoms of gonorrhea include burning sensation while urinating, discharge from the penis, or painful or swollen testicles. Not all men, however, experience symptoms. Most women have mild or no symptoms.

If untreated, gonorrhea can cause serious complications, including infertility in men and women, infection of the urethra or rectum, and problems with pregnancy in women. Babies born to women with untreated gonorrhea can have severe eye infections that lead to blindness.

The WHO is calling for better monitoring of strains of gonorrhea resistant to antibiotics, as well as research into new treatments. It also emphasizes the importance of safe sex in the prevention of new infections. This includes using condoms correctly during sex, and limiting the number of sexual partners.