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Pathology => Human Diseases => Sexually Transmitted Diseases
Sexually Transmitted Diseases
INTRODUCTION
Sexually Transmitted Diseases (STDs), formerly known as venereal diseases, infectious diseases passed from one person to another primarily during sexual contact. STDs are among the most common infections known-more than 12 million people in the United States, including 3 million teenagers, are infected with STDs every year. The United States has the highest STD rate in the industrialized world-roughly one in ten Americans will contract an STD during his or her lifetime.
Some STDs, such as gonorrhea or chlamydia, may cause no symptoms. People who do not know they are infected risk infecting their sexual partners and, in some cases, their unborn children. If left untreated, these diseases may cause debilitating pain or may destroy a woman's ability to have children. Some STDs can be cured with a single dose of antibiotics, but many, such as acquired immune deficiency syndrome (AIDS), are incurable. People with these diseases remain infectious to others for their entire lives.
Those most at risk for contracting STDs are people who have unprotected sex-that is, sex without using a latex condom; those who have multiple partners; and those whose sex partners include intravenous drug users who share needles. Studies show that Americans between the ages of 16 and 24 are at greater risk for acquiring STDs than older adults are, because younger people are more likely to have multiple sexual partners rather than a single, long-term relationship. Additionally, young people may be more likely to have unprotected sex and may be embarrassed to tell their sexual partners they are infected. Young people may also be embarrassed or unable to seek treatment for STDs. This means that they are not only more likely to pass the disease to other young people, they also have a greater risk of suffering the long-term consequences of untreated STDs.
HOW STDS ARE TRANSMITTED
STDs are transmitted by infectious agents-microscopic bacteria, viruses, parasites, fungi, and single-celled organisms called protozoa-that thrive in warm, moist environments in the body, such as the genital area, mouth, and throat. Most STDs are spread during sexual intercourse (vaginal or anal), but other forms of sexual contact, such as oral sex, can also spread disease. Some STDs are passed from an infected mother to her child before birth, when the infection crosses the placenta and enters the baby's bloodstream; during childbirth, as the baby passes through the birth canal; or after birth, when the baby consumes infected breast milk.
Some viral STDs, especially AIDS, may be transmitted by blood. Such STDs may be passed between people who share infected needles or received through a transfusion of infected blood. Some people mistakenly believe that STDs can be transmitted through shaking hands or other casual contact, or through contact with inanimate objects such as clothing or toilet seats. Such transmissions are extremely rare.
COMMON STDS
Chlamydia, caused by the Chlamydia trachomatis bacterium, is the most commonly transmitted STD in the United States. According to the Centers for Disease Control and Prevention (CDC), about 500,000 chlamydia infections are reported each year. But because chlamydia may not produce noticeable symptoms, it often goes undiagnosed, and the CDC estimates that the true incidence of chlamydia is nearly ten times the number of reported cases.
People who do not know they are infected 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 burning urination, vaginal discharge, or mild lower abdominal pain. If left untreated, chlamydia damages reproductive tissue, causing inflammation of the urethra in men and possibly pelvic inflammatory disease (PID) in women. PID can cause chronic, debilitating pelvic pain, infertility, or fatal pregnancy complications. Chlamydia infections are diagnosed by testing penile and vaginal discharge for the presence of the bacteria.
Gonorrhea, caused by the bacteria Neisseria gonorrhoeae, infects the membranes lining certain genital organs. Although roughly 325,000 gonorrhea infections are reported each year in the United States, experts estimate that closer to 800,000 people are infected annually. Like chlamydia, gonorrhea is often symptomless, and men are more likely to develop symptoms than women are. 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 specimens for the presence of Neisseria gonorrhoeae. Gonorrhea is treatable with several antibiotics, although it has become resistant to treatment with many drugs in the past several decades.
Syphilis, a potentially life-threatening STD, is caused by the bacteria Treponema pallidum. According to the CDC, there are an estimated 100,000 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 is easily treated with penicillin, and the number of cases in the United States has dropped considerably since 1982. It is up to ten times more common in some regions of the southern United States than in other parts of the country. 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.
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. The symptoms of HSV can be treated with antiviral drugs, such as acyclovir, but HSV cannot be eradicated from the body-it is incurable.
AIDS, the result of infection with the human immunodeficiency virus (HIV), is an incurable and deadly STD. AIDS attacks the body's immune system, leaving victims open to a wide range of infections. While HIV can be transmitted by other means, sex is the most common means of transmission. Women who are infected with HIV can pass the virus to their infants during 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.
Certain types of hepatitis virus can be spread through sexual contact. One hundred times more contagious than HIV, hepatitis B is spread sexually and during childbirth: Between 90 and 95 percent of all babies born to infected mothers will contract the disease during birth. Hepatitis B attacks liver cells, leading to cirrhosis and possibly 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.
Genital warts, transmitted by the human papilloma virus during sexual contact, grow on the penis and in and around the entrance to the vagina and anus. The CDC estimates that there are 500,000 to 1 million new cases of genital warts in the United States each year. Although they are relatively painless, genital warts significantly increase the risk of cervical cancer in women. Genital warts are treatable with topical medications and can be removed with minor surgical procedures.
Trichomoniasis, caused by infection with the protozoan Trichomonas vaginalis, causes vaginitis, inflammation of the vagina causing burning, itching, and discomfort. In men, trichomoniasis may cause similar problems in the urethra, called urethritis. Trichomoniasis is usually easily treated with a single dose of antibiotics. It is estimated that 3 million Americans are infected with trichomoniasis each year.
PREVENTION AND CONTROL
Unlike many serious diseases, STDs can be prevented by taking simple measures. The most effective prevention method is abstinence-that is, refraining from sex completely. No sexual contact means no risk of developing an STD. Practicing monogamy, in which two partners do not have sexual relations with anyone but each other, also greatly reduces the risk of spreading and contracting STDs.
Latex condoms are an effective, although not perfect, form of protection from STDs. These plastic sheaths, worn over the penis or inserted into the vagina, act as a physical barrier to organisms that cause STDs. However, condoms do not cover all of the genital surfaces that may come into contact during sex, and the possibility of transmission of some STDs, especially genital herpes and warts, still exists.
Early diagnosis and thorough treatment prevent the more serious consequences of infection, while halting the spread of STDs from person to person. This is most critical in STDs that do not cause symptoms, because those infected often do not know they risk infecting their sexual partners. Drug treatment programs must be completed, even if early doses of drugs appear to alleviate symptoms entirely. The infection may still persist in the absence of symptoms, leading infected individuals to unknowingly spread the disease. Furthermore, exposure to small doses of antibiotics that do not kill the infection may enable the infecting agent to develop resistance to the drug.
Public clinics screen patients at risk for STDs in order to diagnose and treat diseases in the early stages. Clinics track the incidence of STDs in particular areas and contact the sexual partners of infected individuals. By identifying and treating these potential carriers, clinics are able to break the chain of STD infections. Several organizations, such as the CDC and the World Health Organization, monitor and research the prevalence and transmission of STDs on an international level in an effort to prevent local outbreaks from reaching global, epidemic proportions.
TRENDS IN STDS
At any time in history, the prevalence and significance of different STDs mirror changes in science and society. For example, in many countries of the world, the incidence of STDs increased during and immediately after World War II (1939-1945), when soldiers spending extended periods of time away from home engaged in unprotected sexual relations with different partners, many of whom carried STDs. When the antibiotic penicillin became widely available in the following years, the same countries experienced dramatic reductions in STD incidence. Beginning in the 1950s, however, the incidence of gonorrhea began to rise as American sexual mores changed. Strains of the disease developed resistance to penicillin, and by the 1970s and 1980s the disease reached epidemic proportions in young adult populations. Introduction of HIV into the human population led to an international crisis that began in the 1980s and continues to this day. Today record numbers of people are infected with genital herpes, and experts suspect that this incurable disease is quickly surpassing chlamydia as the most common STD in the United States.
Cases of STDs are increasing in the late 20th century, even though the use of condoms has increased since the onset of the AIDS epidemic. Public health officials feel that many factors are probably responsible, among them trends in sexual behavior. In the last several decades, the age at which people have sex for the first time has shifted downward, while the average number of partners a person has sex with during his or her lifetime has increased. Together, these trends increase the risk of exposure to an STD.
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