A lot of men with gonorrhea don’t even know they are infected with the sexually transmitted disease. That's dangerous: They have no outward symptoms of the STD, but can still spread the infection to others.

According to Planned Parenthood, one in 10 men with the disease is unaware of the infection. Although that may not sound like much, it may actually be tens of thousands of men; the Centers for Disease Control and Prevention recently released last year’s skyrocketing statistics on STDs, which included 400,000 gonorrhea cases. And even with those who have symptoms, Planned Parenthood says, they may be mild and might only appear in the morning. “That's why many people do not realize they have an infection.”

When they do show up, male symptoms of gonorrhea include a white, yellow or green pus-like discharge from the penis, a burning feeling while urinating and, less commonly, painful or swollen testicles, according to the CDC. But gonorrhea isn’t just spread through vaginal intercourse — it’s also passed during anal or oral sex, which can result in a rectal or oral infection. With the rectum, the CDC says, the symptoms, which may also be hidden, include discharge, itch, bleeding, soreness and painful bowel movements. Oral infections have no symptoms in 90 percent of cases, Planned Parenthood estimates, but can show up as itchiness or soreness in the throat and trouble swallowing.

There’s good news: Gonorrhea is curable with antibiotics. An infected person’s partner should also be treated before having sex again. The CDC warns, however, that some cases are gonorrhea are resistant to drugs, so it’s important to remain vigilant and if symptoms continue despite treatment, “you should return to a health care provider to be checked again.” And any medicine does not make a person immune — anyone can get gonorrhea multiple times through unprotected sex with an infected partner.

Without proper treatment, gonorrhea can cause serious complications. “In men, gonorrhea can cause a painful condition in the tubes attached to the testicles,” according to the CDC. “In rare cases, this may cause a man to be sterile, or prevent him from being able to father a child.” Also in rare cases, the gonorrhea can increase the chance of spreading or contracting HIV.

It can also spread to the blood and other parts of the body, like the joints, which may be life-threatening. The Mayo Clinic explains infected joints could be painful and swollen. That organization also lists the eyes as a possible landing site of gonorrhea, causing pain, light- sensitivity and pus-like discharge.

Worried you might have gonorrhea? It’s easy to get tested through your doctor, Planned Parenthood, or other clinics or health departments. But the best defense against the disease is to use protection while having sex.