context: When you're planning for a hot night under the sheets, you might not want to think about STDs. If you're happily smitten with your long-time partner, you may not think you have to. But the possibility of infections and diseases are as much a part of sex as the fun is. Both men and women get them. Even if you didn't realize it, you've probably had an STD. Knowledge is power when it comes to your sexual health. Recognizing the symptoms is a start, but you won't always notice chlamydia, gonorrhea, herpes, and other STDs. You'll need to get tested to protect yourself -- and your partner. Fortunately, all of these common STDs can be treated, and most can be cured. Nearly every sexually active person will have HPV at some point. It is the most common sexually-transmitted infection in the U. S. More than 40 types of HPV can be spread sexually. You can get them through vaginal, anal, or oral sex. You can get them by skin-to-skin contact, too. Most types of HPV have no symptoms and cause no harm, and your body gets rid of them on its own. But some of them cause genital warts. Others infect the mouth and throat. Still others can cause cancer of the cervix, penis, mouth, or throat. Three vaccines ( Cevarix, Gardasil, Gardasil-9) protect against these cancers. Gardasil and Gardasil-9 also protect against genital warts, vaginal cancer, and anal cancer. The CDC recommends young women and men ages 11 to 26 get vaccinated for HPV. A Pap smear can show most cervical cancers caused by HPV early on. Chlamydia is the most commonly reported STD in the U. S. It's spread mostly by vaginal or anal sex, but you can get it through oral sex, too. Sometimes you'll notice an odd discharge from your vagina or penis, or pain or burning when you pee. But only about 25% of women and 50% of men get symptoms. Chlamydia is caused by bacteria, so it's treated with antibiotics. After you are treated, you should get retested in three months, even if your partner has been treated as well. Gonorrhea is another common bacterial STD. People often get it with chlamydia, and the symptoms are similar: unusual discharge from the vagina or penis, or pain or burning when you pee. Most men with gonorrhea get symptoms, but only about 20% of women do. Gonorrhea is easily treated with antibiotics. Syphilis is a tricky disease with four stages. In the primary stage, the main symptom is a sore. Sometimes syphilis is called the "great imitator" because the sore can look like a cut, an ingrown hair, or a harmless bump. The secondary stage starts with a rash on your body, followed by sores in your mouth, vagina, or anus. Symptoms usually disappear in the third, or latent, stage. This stage can last for years or the rest of your life. Only about 15% of people with untreated syphilis will develop the final stage. In the late stage, it causes organ and nerve damage. It can also cause problems in your brain. Your doctor can give you antibiotics to treat syphilis. The earlier treatment starts, the fewer antibiotics you'll need and the more quickly they work. Both strains of the herpes virus, HSV-1 and HSV-2, can cause genital herpes, but usually the culprit is HSV-2. The main symptom of herpes is painful blisters around the penis, vagina, or anus. But you might get blisters inside your vagina or anus where you can't see or feel them. Not everyone who has herpes gets blisters. Herpes is easy to catch. All it takes is skin-to-skin contact, including areas that a condom doesn't cover. You're most contagious when you have blisters, but you don't need them to pass the virus along. Because herpes is a virus, you can't cure it. But you can take medication to manage it. More women than men get trichomoniasis, which is caused by a tiny parasite. Men and women can give it to each other through penis-vagina contact. Women can give it to each other when their genital areas touch. Only about 30% of people with trichomoniasis have symptoms including itching, burning, or sore genitals. You might also see a smelly, clear, white, yellowish, or greenish discharge. Trichomoniasis is treated with antibiotics. It is important to be retested within three months of treatment, even if your partner has been treated as well. HIV is the virus that causes AIDS. It's passed through body fluids such as blood, semen, vaginal fluids, and breast milk. You can get it by having vaginal or anal intercourse with an infected person without a condom, or by sharing a needle with someone who is infected. You can't get HIV from saliva or by kissing. Symptoms of HIV infection are vague. They can feel like the flu, with muscle aches, fatigue, or a slight fever. You could also lose weight or have diarrhea. The only sure way to tell if you've been infected is to get your saliva or blood tested. HIV can take years to destroy your immune system. Past a certain point, your body loses its ability to fight off infections. There's no cure for HIV, but powerful drugs can help people with HIV live long lives.