Infection transmitted through human sexual behavior
Medical condition
A sexually transmitted infection (STI), also referred to as a sexually transmitted disease (STD) and the older term venereal disease (VD), is an infection that is spread by sexual activity, especially vaginal intercourse, anal sex, oral sex, or sometimes manual sex.[1][5][6] STIs often do not initially cause symptoms,[1] which results in a risk of transmitting them on to others.[7][8] The term sexually transmitted infection is generally preferred over sexually transmitted disease or venereal disease, as it includes cases with no symptomatic disease.[9] Symptoms and signs of STIs may include vaginal discharge, penile discharge, ulcers on or around the genitals, and pelvic pain.[1] Some STIs can cause infertility.[1]
Bacterial STIs include chlamydia, gonorrhea, and syphilis.[1] Viral STIs include genital warts, genital herpes, and HIV/AIDS.[1] Parasitic STIs include trichomoniasis.[1] Most STIs are treatable and curable, of the most common infections; syphilis, gonorrhea, chlamydia, and trichomoniasis are curable, while HIV/AIDS and genital herpes are not curable.[1] Some vaccinations may decrease the risk of certain infections including hepatitis B and few types of HPV.[2]Safe sex practices such as use of condoms, having smaller number of sexual partners, and being in a relationship in which each person only has sex with the other also decreases STIs risk.[1][2]Comprehensive sex education may also be useful.[10]
STI diagnostic tests are usually easily available in the developed world, but they are often unavailable in the developing world.[1] There is often shame and stigma associated with STIs.[1] In 2015, STIs other than HIV resulted in 108,000 deaths worldwide.[4] Globally, in 2015, about 1.1 billion people had STIs other than HIV/AIDS.[3] About 500 million have either syphilis, gonorrhea, chlamydia or trichomoniasis.[1] At least an additional 530 million have genital herpes, and 290 million women have human papillomavirus.[1] Historical documentation of STIs in antiquity dates back to at least the Ebers Papyrus (c. 1550 BCE) and the Hebrew Bible/Old Testament (8th/7th C. BCE).[11]
Signs and symptoms
Not all STIs are symptomatic, and symptoms may not appear immediately after infection. In some instances a disease can be carried with no symptoms, which leaves a greater risk of passing the disease on to others. Depending on the disease, some untreated STIs can lead to infertility, chronic pain or death.[12]
HIV (Human Immunodeficiency Virus)—venereal fluids, semen, breast milk, blood
HPV (Human Papillomavirus)—skin and mucosal contact. 'High risk' types of HPV cause almost all cervical cancers, as well as some anal, penile, and vulvar cancer.[54] Some other types of HPV cause genital warts.
Chlamydia is a sexually transmitted infection caused by the bacterium Chlamydia trachomatis. In women, symptoms may include abnormal vaginal discharge, burning during urination, and bleeding in between periods, although most women do not experience any symptoms.[60] Symptoms in men include pain when urinating, and abnormal discharge from their penis.[61] If left untreated in both men and women, chlamydia can infect the urinary tract and potentially lead to pelvic inflammatory disease (PID). PID can cause serious problems during pregnancy and even has the potential to cause infertility. It can cause a woman to have a potentially deadly ectopic pregnancy, in which the egg implants outside of the uterus. However, chlamydia can be cured with antibiotics.
The two most common forms of herpes are caused by infection with herpes simplex virus (HSV). HSV-1 is typically acquired orally and causes cold sores; HSV-2 is usually acquired during sexual contact and affects the genitals; however, either strain may affect either site.[62] Some people are asymptomatic or have very mild symptoms. Those that do experience symptoms usually notice them 2 to 20 days after exposure which lasts 2 to 4 weeks. Symptoms can include small fluid-filled blisters, headaches, backaches, itching or tingling sensations in the genital or anal area, pain during urination, flu like symptoms, swollen glands, or fever. Herpes is spread through skin contact with a person infected with the virus. The virus affects the areas where it entered the body. This can occur through kissing, vaginal intercourse, oral sex or anal sex. The virus is most infectious during times when there are visible symptoms; however, those who are asymptomatic can still spread the virus through skin contact.[63] The initial infection and symptoms are usually the most severe because the body does not have any antibodies built up. After the primary attack, one might have recurring attacks that are milder or might not even have future attacks. There is no cure for the disease but there are antiviral medications that treat its symptoms and lower the risk of transmission (Valtrex). Although HSV-1 is typically the "oral" version of the virus, and HSV-2 is typically the "genital" version of the virus, a person with HSV-1 orally can transmit that virus to their partner genitally. The virus, either type, will settle into a nerve bundle either at the top of the spine, producing the "oral" outbreak, or a second nerve bundle at the base of the spine, producing the genital outbreak.
The human papillomavirus (HPV) is the most common STI in the United States.[64] There are more than 40 different strands of HPV and many do not cause any health problems. In 90% of cases, the body's immune system clears the infection naturally within two years.[65] Some cases may not be cleared and can lead to genital warts (bumps around the genitals that can be small or large, raised or flat, or shaped like cauliflower) or cervical cancer and other HPV related cancers. Symptoms might not show up until advanced stages. It is important for women to get pap smears in order to check for and treat cancers. There are also two vaccines available for women (Cervarix and Gardasil) that protect against the types of HPV that cause cervical cancer. HPV can be passed through genital-to-genital contact as well as during oral sex. The infected partner might not have any symptoms.
Gonorrhea is caused by bacterium that lives on moist mucous membranes in the urethra, vagina, rectum, mouth, throat, and eyes. The infection can spread through contact with the penis, vagina, mouth, or anus. Symptoms of gonorrhea usually appear two to five days after contact with an infected partner; however, some men might not notice symptoms for up to a month. Symptoms in men include burning and pain while urinating, increased urinary frequency, discharge from the penis (white, green, or yellow in color), red or swollen urethra, swollen or tender testicles, or sore throat. Symptoms in women may include vaginal discharge, burning or itching while urinating, painful sexual intercourse, severe pain in lower abdomen (if infection spreads to fallopian tubes), or fever (if infection spreads to fallopian tubes); however, many women do not show any symptoms.[66] Antibiotic resistant strains of Gonorrhea are a significant concern, but most cases can be cured with existing antibiotics.
Secondary syphilis
Syphilis is an STI caused by a bacterium. Untreated, it can lead to complications and death.[67] Clinical manifestations of syphilis include the ulceration of the uro-genital tract, mouth or rectum; if left untreated the symptoms worsen. In recent years, the prevalence of syphilis has declined in Western Europe, but it has increased in Eastern Europe (former Soviet states). A high incidence of syphilis can be found in places such as Cameroon, Cambodia, Papua New Guinea.[68] Syphilis infections are increasing in the United States.[69]
Trichomoniasis is a common STI that is caused by infection with a protozoan parasite called Trichomonas vaginalis.[70] Trichomoniasis affects bot
