Sexually transmitted infections (STIs) are often called a ‘silent epidemic’ for the very reason that they don’t typically have outward signs

That’s because STDs often show no noticeable symptoms.

This means that you could be infected and not even know it—and same goes for your partner. Read on for four common STDs that might have already snuck up on you, and what you should do about it.

1. GONORRHEA

This bacterial illness is spread through unprotected vaginal, oral, or an*l s*x. As a result, it can cause infections in your private parts, rectum, or throat.

Condoms are nearly 100 percent effective at preventing transmission of the disease, says Khalil Ghanem, M.D., Ph.D., associate professor of medicine and infectious disease at Johns Hopkins University School of Medicine. (Dental dams can be protective if you’re giving oral s*x to a woman.)

Signs of gonorrhea: Women often don’t have any symptoms, says Herbenick. And when they do, the signs are usually mild and may mimic a bladder infection—meaning she may not know she’s infected, and there’s no way for you to tell during s*x.

As for guys: If the infection is in your throat or rectum, you probably won’t have any symptoms, says Dr. Ghanem.

If the bacteria is targeting your man-hood, you may see a greenish or yellowish penile discharge or a burning sensation when you pee, Dr. Ghanem says. Testicular pain is another possibility, although it’s rare. These problems usually creep up 3 to 5 days after an exposure.

Left untreated, gonorrhea can cause something called epididymitis, an inflammation of your testicles that may lead to infertility.

How to detect gonorrhea: The CDC recommends routine annual screenings for men. But ask your doctor what’s right for you, since it may depend on risk factors like how often you have new partners, says Herbenick.

How to treat gonorrhea: The good news is that gonorrhea can usually be cured with antibiotics.

But Some Gonorrhea Strains Are Resistant To Antibiotics, so make sure to follow up with your doctor to make sure all the bacteria has been killed, says Herbenick.