Sexually Transmitted Diseases | Clinical Study About STDs

Sexually transmitted diseases (STDs) have been well known since the writings of Hippocrates. Here we discuss three bacterial STDs—gonorrhea, chlamydia, and syphilis—and three viral STDs—genital herpes, genital warts, and hepatitis. All of these STDs have an incubation period in which the pathogen multiplies without symptoms, and a communicable period in which one can transmit the disease to others, even in the absence of symptoms. STDs often cause fetal deformity, stillbirth, and neonatal death.

Gonorrhea is caused by the bacterium Neisseria gonorrhoeae. Galen, thinking the pus discharged from the penis was semen, named the disease gonorrhea (“flow of seed”). Gonorrhea causes abdominal discomfort, genital pain and discharge, painful urination, and abnormal uterine bleeding, but most infected women are asymptomatic. It can cause scarring of the uterine tubes, resulting in infertility. Gonorrhea is treated with antibiotics.
Nongonococcal urethritis (NGU) is any urethral inflammation caused by agents other than the gonorrhea bacterium. NGU often produces pain or discomfort on urination. The most common bacterial NGU is chlamydia, caused by Chlamydia trachomatis. Most chlamydia infections are asymptomatic, but they may cause urethral discharge and pain in the testes or pelvic region. Gonorrhea and chlamydia frequently occur together.

Pelvic inflammatory disease (PID) is acute, painful inflammation of the female pelvic organs, usually due to infection with Chlamydia or Neisseria. It often causes irregular menstrual bleeding or pain on urination. It can result in sterility and may require surgical removal of infected uterine tubes or other organs. PID is responsible for many cases of ectopic pregnancy.
Syphilis is caused by a spiral bacterium named Treponema pallidum. After an incubation period of 2 to 6 weeks, a small, hard lesion called a chancre appears at the site of infection—in males, usually on the penis, but in females, sometimes out of sight in the vagina. It disappears in 4 to 6 weeks, ending the first stage of syphilis and often creating an illusion of recovery. A second stage ensues, however, with a widespread pink rash, other skin eruptions, fever, joint pain, and hair loss. This subsides in 3 to 12 weeks, but symptoms can come and go for up to 5 years. A person is contagious even when symptoms are not present. The disease may progress to a third stage, tertiary syphilis (neurosyphilis), with cardiovascular damage and brain lesions that can cause paralysis and dementia. Syphilis is treatable with antibiotics.
Genital herpes is the most common STD in the United States, with 20 to 40 million infected people. It is usually caused by the herpes simplex virus type 2 (HSV-2). After an incubation period of 4 to 10 days, the virus causes blisters on the penis of the male; on the labia, vagina, or cervix of the female; and sometimes on the thighs and buttocks of either sex. Over 2 to 10 days, these blisters rupture, seep fluid, and begin to form scabs. The initial infection may be painless or may cause intense pain, urethritis, and watery discharge from the penis or vagina. The lesions heal in 2 to 3 weeks and leave no scars.

During this time, however, HSV colonizes sensory nerves and ganglia. Here it can lie dormant for years, later migrating along the nerves and causing epithelial lesions anywhere on the body. The movement from place to place is the basis of the name herpes.37 Most patients have five to seven recurrences, ranging from several years apart to several times a year. An infected person is contagious to a sexual partner when the lesions are present and sometimes even when they are not. HSV may increase the risk of cervical cancer and AIDS.

Genital warts (condylomas) are caused by various strains of human papillomavirus (HPV). In most cases, HPV infection goes away on its own and does not cause any health problems. If it persists, however, it can cause genital warts or worse. In the male, warts usually appear on the penis, perineum, or anus; and in the female, they are usually on the cervix, vaginal wall, perineum, or anus. Lesions are sometimes small and almost invisible. Genital warts can be treated with cryosurgery (freezing and excision), laser surgery, or interferon.

An HPV vaccine became available in 2006 and infection rates in young people seem to be declining as a result of vaccination. Certain strains of HPV different from those that usually cause genital warts cause cancer of the penis, vagina, cervix, anus, and throat; nearly all cervical cancer and about 70% of throat cancer is caused by HPV. There are about 14 million new cases of HPV infection in the United States per year. Given the alarming incidence of sexual
activity and HPV among young adolescents, the U.S. Food and Drug Administration recommends vaccination of girls and boys at the age of puberty in hopes of immunizing most before the onset of sexual activity.

Hepatitis B and C are inflammatory liver diseases caused by the hepatitis B and C viruses (HBV, HCV). Although they can be transmitted by means other than sex, they are becoming increasingly common as STDs. Hepatitis C threatens to become a major epidemic of the twenty-first century. It already far surpasses the prevalence of AIDS and is the leading reason for liver transplants in the United States.
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