Overview of Sexually Transmitted Diseases
Sexually transmitted diseases (STDs), also termed sexually transmitted infections (STIs), can be caused by a number of microorganisms that vary widely in size, life cycle, symptoms, and susceptibility to available treatments.
Bacterial STDs include
Viral STDs include
Parasitic infections that can be sexually transmitted include
Many other infections not considered primarily to be STDs—including salmonellosis, shigellosis, campylobacteriosis, amebiasis, giardiasis, hepatitis (A, B, and C), and cytomegalovirus infection—can be transmitted sexually.
Because sexual activity includes close contact with skin and mucous membranes of the genitals, mouth, and rectum, many organisms are efficiently spread between people. Some STDs cause inflammation (eg, in gonorrhea or chlamydial infection) or ulceration (eg, in herpes simplex, syphilis, or chancroid), which predispose to transmission of other infections (eg, HIV).
STD prevalence rates remain high in most of the world, despite diagnostic and therapeutic advances that can rapidly render patients with many STDs noninfectious. In the US, an estimated 20 million new cases of STDs occur each year; about half occur in people aged 15 to 24 yr (see also Reported STDs in the United States: 2014 National Data for Chlamydia, Gonorrhea, and Syphilis).
Factors impeding control of STDs include
Unprotected sexual activity with multiple partners
Difficulty talking about sexual issues for both physicians and patients
Inadequate funding for implementing existing diagnostic tests and treatments and for developing new tests and treatments
Susceptibility to reinfection if both partners are not treated simultaneously
Incomplete treatment, which can lead to development of drug-resistant organisms
International travel, which facilitates rapid global dissemination of STDs
Symptoms and signs vary depending on the infection. Many STDs cause genital lesions (see Table: Differentiating Common Sexually Transmitted Genital Lesions).
Differentiating Common Sexually Transmitted Genital Lesions
STDs are diagnosed and treated in a variety of settings; for many, diagnostic tests are limited or unavailable or patient follow-up is uncertain. Thus, identification of the causative organism is often not pursued. Often, diagnosis is based only on clinical findings.
Diagnostic testing may include Gram staining and culture or laboratory tests such as nucleic acid amplification tests (NAATs). Diagnostic testing is done more often in the following situations:
Because diagnostic tests are often limited or unavailable and/or patient follow-up is uncertain, initial treatment is often syndromic—ie, directed at the organisms most likely to cause the presenting syndrome (eg, urethritis, cervicitis, genital ulcers, pelvic inflammatory disease).
Most STDs can be effectively treated with drugs. However, drug resistance is an increasing problem.
Patients who are being treated for a bacterial STD should abstain from sexual intercourse until the infection has been eliminated from them and their sex partners. Sex partners should be evaluated and treated simultaneously.
Viral STDs, especially herpes and HIV infection, usually persist for life. Antiviral drugs can control but not yet cure all of these infections.
STD control depends on
Adequate facilities and trained personnel for diagnosis and treatment
Public health programs for locating and treating recent sex partners of patients
Follow-up for treated patients to ensure that they have been cured
Education of health care practitioners and the public
Avoidance of high-risk behaviors by patients
Condoms and vaginal dams, if used correctly, greatly decrease risk of some STDs.
Vaccines are unavailable for most STDs, except for hepatitis A and B and human papillomavirus infection.