Here’s a scary stat that could make you lose your boner: About 20 million new sexually transmitted infections occur every year, according to the Centres for Disease Control. The whole trick to not being one of ’em? Exactly what you learned in eighth grade health class: Practice safe sex and stay up to date on tests. For motivation, a quick refresher on what five major STIs look like — and what can happen if you don’t treat them appropriately.
What it is: The virus that causes Acquired Immunodeficiency Syndrome (AIDS). It attacks your immune system by destroying an important type of white blood cell that works to fight off infections in the body. If you’re infected with HIV (via unprotected sex with someone who has the virus or through contact with other bodily fluids, including blood), you’re more vulnerable to infections and diseases that a healthy immune system would normally fight off. The CDC recommends everyone between the ages of 13 and 64 get tested at least once in their life, and those who are at a higher risk (gay, bisexual, or other men who have sex with men) get tested more frequently than that — annually in some cases.
Initial symptoms: In the weeks following infection, HIV symptoms might look like those of mononucleosis, says Pritish Tosh, MD, an infectious diseases physician and researcher at the Mayo Clinic. Think a fever, sore throat, rash, or simply feeling pretty under the weather.
If left untreated: Those symptoms often then subside — even for years while the virus slowly chips away at your immune system. Eventually, you might come down with an infection that people with healthy immune systems shouldn’t be getting, Tosh explains. By that time, the virus might be advanced. Depending on that new infection, symptoms might include fever, weight loss, or a dry cough, Tosh notes.
HIV can also progress to AIDs and even be deadly, Tosh notes, adding: “HIV is probably the most devastating sexually transmitted [infection].”
Treatment: Antiretroviral therapy. “Treatments of HIV have progressed to the point that once someone is diagnosed and taking medications reliably, we would expect them to be able to live a normal life,” Tosh says. “We can, in some ways, reverse the damage done by HIV.” Of course, in order to do this, you have to (a) get diagnosed and (b) take your medication regularly.
GONORRHEA AND CHLAMYDIA
What they are: Sexually transmitted infections (STIs) caused by bacteria — Neisseria gonorrhoeae and Chlamydia trachomatis, respectively — and spread by vaginal, anal, or oral sex. The CDC recommends annual screening for both.
Initial symptoms: Most commonly urethritis, an inflammation of the urethra, which can result in a painful, burning feeling when you pee. But both can also be asymptomatic, Tosh notes.
If left untreated: If they progress, these STIs can also lead to more serious infections around the testes. In rare cases, gonorrhea can also spread throughout the body where it can infect the joints, causing damage and pain within weeks of infection.
You can also pass the infections onto a sexual partner. And in women, both untreated gonorrhea and chlamydia can progress into pelvic inflammatory disease, an infection in the female reproductive organs, and can lead to infertility. For men, in rare cases and depending on the severity of the infection, both can potentially lead to infertility as well, Tosh adds.
HUMAN PAPILLOMAVRIUS (HPV)
What it is: A group of 150+ related viruses spread via vaginal, anal, or oral sex.
Initial symptoms: Often, none.
If left untreated: The STI can cause oral and penile cancers in men, Tosh says. Some types (often not the ones that cause cancer) can also lead to genital warts.
Treatment: There is no treatment for HPV itself, but genital warts can be treated or removed if they’re bothersome. Using condoms can lower your chances of getting infected or of spreading the disease.
If you didn’t get the HPV vaccine as a kid, know that the CDC recommends it for all men through age 21. If you’re gay or bisexual or you have a weakened immune system, the CDC recommends it through age 26.
RELATED: 4 STD’s You Might Already Have
What it is: Two types of viruses: herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) spread by vaginal, anal, or oral sex, as well as through contact with a herpes sore or with the saliva or genital secretions of someone with the infection.
Initial symptoms: Most people infected with HSV-1 have no idea that they have herpes. The immune system is able to handle the virus so that it doesn’t result in cold sores, says Tosh. With HSV-2, the most common symptom is genital sores, though only a fraction of infected people have symptoms.
If left untreated: Generally speaking, herpes causes more embarrassment than serious health concerns, Tosh says. But if you’re suffering from herpes outbreaks and not treating them, they can continue or get worse. The bigger issue with not treating outbreaks is that you could pass the virus along to a partner.
Treatment: There is no cure for herpes, but people with recurrent outbreaks—cold sores or genital ones—can benefit from anti-virals, which can help lessen the outbreaks’ severity. When taken daily, these meds can also lower the likelihood that you’ll pass herpes onto a sexual partner.
This article originally appeared on Men’s Health