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The facts about STIs

Almost 20 million people in the United States contract—and more than 2 million are diagnosed with—a sexually transmitted infection (STI) each year.

Of the nearly 20 million people who contract a sexually transmitted infection (STI) each year, almost half are between the ages of 15 and 24, according to the Centers for Disease Control and Prevention (CDC). The only surefire way to avoid STIs is abstinence (no sexual activity). If you choose to be sexually active, many strategies can reduce your risk of STIs.

Diseases, symptoms, dangers

Causes, symptoms, treatments and prevention methods may vary depending on the type of STI. The facts about some well-known STIs are outlined below.

  • Syphilis

    Symptoms: A small, single, firm but painless sore (chancre) marks the primary phase of syphilis. In the secondary phase, the chancre disappears and a rash appears, often on the hands and feet. Other symptoms can include fever, swollen glands, sore throat, headache and muscle aches.

    Spread by: Direct contact with the chancre, which often appears in the genital area or sometimes the mouth.

    Treated with: Penicillin.

    Complications: Severe damage to internal organs, blindness, dementia, death and transmission to fetus.

    To reduce your risk: Limit your number of sex partners, use latex condoms.

  • Gonorrhea

    Symptoms: Often none, especially in women. In men, symptoms can include a burning sensation during urination, yellow-white discharge from the penis and painful testicles. Women also may experience painful urination and yellow or bloody vaginal discharge. Infections in the rectal area can cause itching, bleeding and soreness.

    Spread by: Sexual contact.

    Treated with: Antibiotics.

    Complications: Pelvic inflammatory disease (PID), a testicular disease called epididymitis, infertility, death and transmission to fetus.

    To reduce your risk: Limit partners, use latex condoms.

  • Chlamydia

    Symptoms: Usually none, but can resemble gonorrhea.

    Spread by: Sexual contact.

    Treated with: Antibiotics.

    Complications: PID, infertility, bladder infection and transmission during birth.

    To reduce your risk: Limit partners, use latex condoms.

    Note: Chlamydia is one of the most frequently reported infectious diseases in the United States, according to CDC. It is especially common among adolescents. As many as 1 in 20 sexually active women between 14 and 24 are infected.

  • Genital herpes

    Symptoms: There are two types of herpes simplex virus (HSV), both of which may have no symptoms at all. When present, symptoms can include lesions or blisters on the mouth or face (HSV-1) or in the genital area (HSV-2). Herpes blisters often come and go.

    Spread by: Sexual contact, including kissing.

    Treated with: Incurable, but blister outbreaks can be shortened or prevented with antiviral medication.

    Complications: Genital blisters can be painful, transmission during birth.

    To reduce your risk: Limit partners. Use latex condoms and abstain from sex during outbreaks.  

  • Human papillomavirus (genital warts)

    Symptoms: There are many different types of human papillomavirus (HPV). Certain types cause warts in the genital area, anus or cervix. HPV often has no symptoms.

    Spread by: Sexual contact.

    Treated with: HPV infection has no cure. Warts can be treated with surgery or medications.

    Complications: HPVs are the leading cause of cervical cancer. Other, mostly genital, cancers also may be associated with HPV infection. However, not all types of HPV cause cancer.

    To reduce your risk: Limit partners, use condoms and get vaccinated. A vaccine is available that protects against many strains of HPV.

  • Crabs (pubic lice)

    Symptoms: These parasites often cause an allergic itching in the pubic area, and sometimes can be seen with the naked eye. They are tiny and crab-like, often white-gray or rust-colored. They also can appear in other hairy areas, such as armpits, eyelashes or scalp.

    Spread by: Skin-to-skin contact with an infected person, sleeping in an infested bed.

    Treated with: Creams, shampoos, rinses. Infested linens, clothing, etc., must be washed in hot water or, if not washable, placed in plastic bags for two weeks.

    Complications: Infection from scratching.

    To reduce your risk: Limit partners.

  • Trichomoniasis

    Symptoms: Another parasite that can infect the vagina or male urethra, often with no symptoms. Men may experience penile irritation, discharge or burning with urination or ejaculation. Women may have yellow-green vaginal discharge with a strong odor, irritation or itching of genital area, or discomfort during urination or intercourse.

    Spread by: Sexual contact of penis to vagina or vulva to vulva.

    Treated with: Medication.

    Complications: Can lead to premature delivery in pregnant women.

    To reduce risks: Limit partners, use latex condoms.

    Note: This is the most common curable STI.

Other important information

Having any STI increases the risk of acquiring HIV because:

  • High-risk sexual behavior is a common risk factor for both STIs and HIV.
  • STIs can accelerate transmission of HIV.

It's important to notify your sexual partner(s) if you have a sexually transmitted infection. Many of these diseases have no symptoms, and people who don't know they have an STI can infect others. Also, the longer a person has an untreated STI, the more likely he or she is to develop complications, some of which can't be reversed.

If you think you are at risk for having an STI, see your doctor or healthcare provider. You also can get more information about STIs from the American Sexual Health Association.

Reviewed 11/10/2021

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