Sexually transmitted diseases (STDs) are infectious diseases that are spread through sexual contact. STDs are on the rise, possibly due to more sexually active people who have multiple sex partners during their lives. The Centers for Disease Control and Prevention (CDC) estimates that 19 million new cases of STDs occur annually in the U.S. STDs affect men and women of all backgrounds and economic levels. Fifty percent of the new infections occur in people between the ages of 15 and 24 years. Types According to the CDC and the National Institute for Allergy and Infectious Diseases, common types of STDs include the following: Acquired immune deficiency syndrome (AIDS): AIDS is caused by the human immunodeficiency virus (HIV), which destroys the body’s ability to fight off infection. People who have AIDS are very susceptible to many life-threatening diseases and to certain forms of cancer. Transmission of the virus most often occurs during sexual activity or by the sharing of needles used to inject intravenous drugs. Human papillomavirus (HPV): This common STD can cause genital warts, which can occur on the inside or outside areas of the genitals and may spread to the surrounding skin or to a sexual partner. Because HPV infection doesn’t always cause warts, the infection may go undetected. There are many different strains of HPV and some strains of the virus can cause dangerous gene mutations within infected cells. Women with an HPV infection have an increased risk of developing cervical cancer. Regular Pap tests can detect HPV infection as well as abnormal cervical cells. An HPV vaccine is available to help prevent cervical cancer. The vaccine, which protects against nine different HPV strains, is also effective at preventing long-term HPV infection, genital warts, precancerous changes, and other types of cancer (anal, vaginal, vulvar and others). Although there is treatment for genital warts, the virus remains and warts can reappear. Chlamydial infections: The most common of all STDs, chlamydial infections can affect both men and women. They may cause an abnormal genital discharge and burning with urination. In women, untreated chlamydial infection may lead to pelvic inflammatory disease (PID). Chlamydial infections can be treated with antibiotic therapy. Unfortunately, many people have few or no symptoms of infection. The most common and serious complications occur in women and include PID, ectopic (tubal) pregnancy, and infertility. Gonorrhea: Gonorrhea causes a discharge from the vagina or penis and painful or difficult urination. The most common and serious complications occur in women, and include PID, ectopic (tubal) pregnancy, and infertility. Gonorrhea infections can be treated with antibiotic therapy. Genital herpes: This infection is caused by the herpes simplex virus (HSV). Symptoms may include painful blisters or open sores in the genital area, which may be preceded by a tingling or burning sensation in the legs, buttocks, or genital region. The sores usually disappear within a few weeks, but the virus remains in the body and the lesions may recur. There is no cure for HSV, but there are anti-viral agents that can shorten an outbreak and reduce symptoms. Syphilis: The initial symptom is a painless open sore that usually appears on or around the sexual organs. Untreated syphilis may advance to a transient rash and, eventually, serious involvement of the heart and central nervous system. Syphilis infections can be treated with antibiotic therapy. It's important to recognize that individuals infected with one STD are likely to harbor other STDs. That's why it's important that a comprehensive sexual health evaluation be performed to identify other untreated STDs. Other diseases that may be sexually transmitted include bacterial vaginosis, chancroid, pubic lice, scabies, trichomoniasis, and vaginal yeast infections. Diagnosis Most STDs can be diagnosed through an exam by your doctor, a culture of the secretions from your vagina or penis, or a blood test. When diagnosed early, many STDs can be successfully treated. Treatment If you’re diagnosed with an STD, begin treatment immediately, take the full course of medications, and follow your doctor’s advice. Avoid sexual activity while you’re being treated, and notify all recent sexual partners and urge them to get medical checkups. Have a follow-up test to be sure the STD has been successfully treated.