III.

Common STIs

The most common STIs in the United States include chlamydia, gonorrhea, syphilis, herpes, AIDS, hepatitis, genital warts, and trichomoniasis.

A.

Chlamydia

According to the Centers for Disease Control and Prevention (CDC), chlamydia is the most frequently reported infectious disease in the United States. Caused by the Chlamydia trachomatis bacterium, the disease does not produce noticeable symptoms in 75 percent of women and 50 percent of men, so an infection often goes undiagnosed. Experts estimate that 3 million people become infected with chlamydia each year, but according to the CDC, only about 660,000 of these infections are reported each year.

People who do not know they are infected with chlamydia may not seek medical care and they may continue to have sex, unknowingly spreading the disease. When symptoms do develop, men may experience painful or burning urination or a discharge from the penis. Women may experience bleeding between periods, burning urination, vaginal discharge, or mild lower abdominal pain. If left untreated in women, chlamydia can cause severe health problems. Chlamydia damages female reproductive tissue, causing pelvic inflammatory disease (PID). PID can cause chronic, debilitating pelvic pain, infertility, or fatal pregnancy complications. Babies born to mothers infected with chlamydia are at risk of developing eye and lung infections.

Diagnosing chlamydia infections requires a physical examination in which a health-care provider performs a pelvic examination to collect a small amount of vaginal or penile fluid, which is then tested for the presence of Chlamydia trachomatis. New diagnostic tests that use urine samples to identify the presence of the chlamydia bacteria have become available, providing a noninvasive way to diagnose people who show no symptoms for the disease. Chlamydia is treatable with antibiotics.

B.

Gonorrhea

Gonorrhea, caused by the bacterium Neisseria gonorrhoeae, infects the membranes lining certain genital organs. Although roughly 360,000 gonorrhea infections are reported each year in the United States, experts estimate that closer to 650,000 people are infected annually. Like chlamydia, gonorrhea is often symptomless. When present, symptoms may be similar to those of chlamydia and include burning urination and penile or vaginal discharge. Untreated gonorrhea can cause PID in women. Babies born to mothers with gonorrhea are at risk of infection during childbirth; such infections can cause eye disease in the newborn. Physicians diagnose gonorrhea by testing penile or vaginal discharge or urine specimens for the presence of Neisseria gonorrhoeae. Gonorrhea is treatable with several antibiotics, although the infection has become resistant to treatment with some drugs in the past several decades.

C.

Syphilis

Syphilis, a potentially life-threatening STI, is caused by the bacterium Treponema pallidum. According to the CDC, there are an estimated 36,000 new cases of syphilis in the United States each year. In the early stage of syphilis, a genital sore, called a chancre, develops shortly after infection and eventually disappears on its own. If the disease is not treated, the infection can progress over years, affecting the vertebrae, brain, and heart, and resulting in such varied disorders as lack of coordination, meningitis, and stroke. Syphilis during pregnancy can be devastating to the fetus, causing deformity and death, and most pregnant women in the United States receive screening for the disease in the first weeks of pregnancy so that the disease can be treated before the fetus is harmed. Syphilis is easily treated with penicillin, and the number of cases in the United States has dropped considerably since 1982. By the late 1990s, however, many urban communities experienced a resurgence in syphilis cases among men who have sex with men.

D.

Genital Herpes

Genital herpes is caused by infection with the herpes simplex virus (HSV). Most cases of genital herpes are due to HSV type 2. Some cases, however, result from genital infections with HSV type 1, a common cause of cold sores. Genital herpes causes recurrent outbreaks of painful sores on the genitals, although the disease often remains dormant with no symptoms for long periods. In the United States, one in five individuals over the age of 12 is infected with HSV type 2, and the vast majority of those infected—about 90 percent—do not know they have the disease. Blood tests can detect HSV infection, even if a person has no symptoms. The symptoms of HSV can be treated with antiviral drugs, such as acyclovir, but HSV cannot be eradicated from the body—it is incurable.

E.

AIDS

AIDS, the result of infection with the human immunodeficiency virus (HIV), is an incurable and deadly STI. AIDS attacks the body’s immune system, leaving victims unable to fight off even the mildest infections. While HIV can be transmitted by other means, sexual contact is the most common means of transmission. Women who are infected with HIV can pass the virus to their infants during pregnancy, childbirth or, less frequently, in breast milk. Treatment options for people infected with HIV include protease inhibitors, which can markedly increase survival. In spite of widespread educational and prevention programs, the CDC estimates that there are 40,000 new cases of HIV each year in the United States and that 800,000 to 900,000 Americans overall have HIV infection.

F.

Hepatitis B

One hundred times more contagious than HIV, hepatitis B passes from person to person through unprotected sexual intercourse with an infected person, or through the sharing of infected needles or other sharp instruments that break the skin. Hepatitis B can also spread during childbirth: Between 90 and 95 percent of all babies born to infected mothers get the disease during birth. The CDC estimates that 120,000 new hepatitis B infections occur each year. Hepatitis B attacks liver cells, sometimes leading to cirrhosis and cancer of the liver. In most cases hepatitis B is incurable, but arduous chemotherapy can eliminate the virus in some patients. There is a safe, effective vaccination for hepatitis B, and most states are developing or already have initiated public school immunization programs.

G.

Genital Warts

Genital warts grow on the penis and in and around the entrance to the vagina and anus. They are caused by a family of viruses known as human papillomavirus (HPV) that are transmitted during sexual intercourse. The CDC estimates that there are 5.5 million new cases of genital warts in the United States each year. Genital warts are treatable with topical medications and can be removed with minor surgical procedures. Certain types of HPV that cause genital infections can also cause cervical cancer. Regular pap smear screenings can detect abnormalities at an early stage, when they can more easily be treated to prevent cancer developing. The first vaccine against HPV strains that can cause genital warts and cervical cancer was approved by the U.S. Food and Drug Administration and by Health Canada in 2006. Sold under the brand name Gardasil, the new vaccine completely prevented infections in women in nearly all clinical trials.

H.

Trichomoniasis

Trichomoniasis, caused by infection with the protozoan Trichomonas vaginalis, causes burning, itching, and discomfort in the vagina in women and the urethra in men. Trichomoniasis is easily treated with a single dose of antibiotics. The CDC estimates that 5 million Americans become infected with trichomoniasis each year.