Overview of STIs

Related Diseases & Conditions

• Genital tract chlamydia infection

  Summary

  Chlamydial genital infection is the most frequently reported STI in the US.[1] [2]​​​ Infection is usually asymptomatic in both men and women.[2]​ Nonculture diagnostic techniques such as nucleic acid amplification tests are recommended.[1] [2]​ In women, there may be cervical inflammation or yellow, cloudy discharge from the cervical os, resulting in vaginal discharge. In men, there may be a discharge from the penis. Typical risk factors include age under 25 years, sexual activity with an infected partner, a new sex partner or multiple sex partners, a sex partner with other concurrent sex partners, history of a prior STI, and not using condoms. Lack of or inadequate treatment risks possible ascending infection and further complications, as well as possible spread of the infection to sexual partners.
• Gonorrhea infection

  Summary

  The most commonly reported STI after chlamydial infection.​​ Over 82.4 million people were infected with gonorrhea in 2020.[3] ​Classic presentation is a man with a urethral discharge; women are often asymptomatic but may have vaginal discharge.[2]​ Key risk factors include age 15 to 24 years, black ancestry, current or prior history of STI, multiple recent sexual partners, inconsistent condom use, men who have sex with men, risk factors of partner, and a history of sexual or physical abuse. If left untreated, Neisseria gonorrhoeae can disseminate to cause skin and synovial infections. Rarer complications include meningitis, endocarditis, and perihepatic abscesses. High rates of antimicrobial resistance have been reported.[3] Nucleic acid amplification tests, culture, Gram stain, and urinalysis form the mainstay of diagnostic laboratory tests for N gonorrhoeae.[2]
• Syphilis infection

  Summary

  A common sexually transmitted infection caused by the spirochetal bacterium Treponema pallidum, subspecies pallidum. Entry of the T pallidum organism into tissues probably occurs via areas of minor abrasion (at genital and mucous membrane sites) that result from trauma during sexual intercourse. Oro-genital sex is an important route of transmission and, therefore, transmission can occur despite the use of condoms.[4] [5]​​​​ There were an estimated 6 million new cases of syphilis worldwide in 2016.[6]​ Clinical presentation is often asymptomatic but can manifest in a number of ways - a painless ulcer (chancre) in the anogenital region is a hallmark of primary infection.[2]​ Diagnosis is usually straightforward after clinical exam and serologic testing. Untreated syphilis facilitates HIV transmission and causes considerable morbidity, such as cardiovascular and neurologic disease, as well as a congenital syndrome in newborn babies.[7]
• Lymphogranuloma venereum

  Summary

  Lymphogranuloma venereum (LGV) is caused by Chlamydia trachomatisgenovars/serovars L1, L2, or L3. LGV may occur at any age, but the peak incidence is between 15 and 40 years, the ages when sexual activity is at its peak.[8] ​Infection occurs through contact with mucous membranes or abrasions in the skin. Sexual transmission is the most common route, but extra-genital sites may be affected when inoculated by non-sexual contact, accidental laboratory inhalation or when transmitted by exposure to fomites. The primary manifestation of infection is a painless penile or vulvar inflammation and ulceration at the site of inoculation, often unnoticed by the patient.[9]​​​​ May present with proctocolitis or tender, unilateral inguinal or femoral lymphadenopathy.[2]​ Risk factors include other STIs and unprotected intercourse in an area endemic for LGV (most notably tropical regions of Southeast Asia, Latin America, the Caribbean, and Africa). Chronic inflammation can lead to scarring and fibrosis causing lymphedema of the genitals, or formation of strictures and fistulae if anorectal involvement. Diagnosis is based on clinical suspicion, careful history taking and physical examination, and exclusion of other etiologies, with a definitive diagnosis confirmed by appropriate microbiologic testing (such as nucleic acid amplification testing, Gram stain, or LGV-specific molecular testing).[2]​ 
• Chancroid

  Summary

  A sexually transmitted infection caused by the fastidious, gram-negative coccobacillus Haemophilus ducreyi, which is most common in resource-poor countries.[10] ​​It is a strictly human pathogen that is transmitted person to person, primarily via unprotected sex, or by auto-inoculation. It can infect skin, mucosal surfaces, and lymph nodes. Classically presents with the acute onset of a painful genital ulcer with fluctuant lymphadenitis (bubo formation).[2]​ Key risk factors include multiple sex partners, sexual contact with a sex worker, unprotected intercourse, substance abuse, male sex, and a lack of circumcision (in men). Chancroid is an important cofactor in HIV transmission, and HIV status must be assessed.
• Pelvic inflammatory disease

  Summary

  An acute ascending polymicrobial infection of the female upper genital tract that is frequently associated with N gonorrhoeae or C trachomatis.[11]​ C trachomatis is thought to be the most common cause of PID and is associated with 14% to 35% of cases.[12] [13]​​​​​​ In industrialized countries, the annual incidence of pelvic inflammatory disease (PID) peaks in women ages 20 to 24 years. Pelvic inflammatory disease includes endometritis, salpingitis, tubo-ovarian abscess, and pelvic peritonitis.[2]​ May be asymptomatic or present with fever, vomiting, back pain, dyspareunia, bilateral lower abdominal pain/discomfort, abnormal vaginal odor, itching, bleeding, or discharge.[11]​ ​Diagnosis may be difficult because symptoms range from absent to severe and may be non-specific. Possible laboratory findings include abundant white blood cells on saline microscopy of vaginal secretions, elevated erythrocyte sedimentation rate, elevated C-reactive protein, and laboratory documentation of cervical infection with N gonorrhoeae or C trachomatis. Laparoscopy is the definitive procedure but is invasive and is not recommended for routine diagnosis.
• Urethritis

  Summary

  Typically presents with dysuria, urethral discharge, and/or pruritus at the end of the urethra. N gonorrhoeae and C trachomatis are the most common causes.​​ Worldwide, in 2020, there were an estimated 82 million cases of gonorrhea infection and 129 million cases of chlamydia infection, commonly presenting as urethritis in men and cervicitis in women.[14] Unprotected vaginal, anal, and insertive oral sex have all been associated with urethritis.[15] ​Key risk factors include age between 15 and 24 years, female sex, new or multiple sex partners, prior or current STI, and inconsistent use of condoms.​ Diagnostic tests include Gram stain and culture of the urethral discharge and nucleic acid amplification tests.[2]
• Cervicitis

  Summary

  Common and often asymptomatic, but if left undiagnosed or untreated can result in PID, which can in turn lead to substantial long-term effects such as infertility and chronic pelvic pain. While N gonorrhoeae and C trachomatis are the most commonly isolated organisms, in most cases no etiologic organism is identified.​ Non-infectious causes include vaginal bacterial overgrowth, local trauma, malignancy, radiation, chemical irritation, vaginal douches, systemic inflammatory diseases, or idiopathic inflammation.[16] ​Common presentations of cervicitis include: dysuria and associated vaginal discharge, pruritic vaginal discharge, dyspareunia, intermenstrual or postcoital bleeding.[2]​ Risk factors include age 15 to 24 years, inconsistent condom use, multiple or new sexual relationships, previous sexually transmitted infections, bacterial vaginosis, sex worker, or absence of hydrogen peroxide-producing lactobacilli.
• Vaginitis

  Summary

  Inflammation of the vagina due to changes in the composition of the vaginal micro-environment from infection, irritants, or hormonal deficiency (e.g., atrophic vaginitis). Vaginitis is the most common gynecological diagnosis in the primary care setting.[17]​ Common symptoms include discharge, pruritus, and dyspareunia. Bacterial vaginosis is the leading cause of vaginitis; other common infectious causes include trichomoniasis and candidiasis.[18] ​An overgrowth of anaerobic bacterial organisms such as Gardnerella vaginalis, Prevotella species, Mobiluncus species, Atopobium vaginae and Megasphaera type 1 is the main cause of bacterial vaginosis.[19]​ Strong risk factors include: douching; poor or excessive hygiene; prior antibiotic use; HIV infection; diabetes mellitus; black women; presence of IUD; use of the oral contraceptive pill; women of reproductive age; menopause; and sexual activity.
• Acute epididymitis

  Summary

  Inflammation of the epididymis characterized by scrotal pain and swelling of less than 6 weeks' duration.[20]​ In sexually active men, epididymitis is most commonly caused by N gonorrhoeae, C trachomatis, or Mycoplasma genitalium.[21] Epididymitis may present at any age, with the majority of patients ages 20 to 39 years.[22]​ In older men (>35 years), the causative organisms are often enteric pathogens, and epididymitis may be associated with bladder outlet obstruction, recent instrumentation of the urinary tract, or systemic illness. Diagnostic tests include a Gram stain of urethral secretions, and urine specimens for nucleic acid amplification tests for C trachomatis, N gonorrhoeae, and M genitalium (where available). Urine microscopy and culture is also indicated if urinary pathogens are suspected. Strong risk factors include: multiple sex partners, partners infected with C trachomatis, N gonorrhoeae, and/or M genitalium; history of anal intercourse; history of viral infection; or infection or contact with tuberculosis.
• Herpes simplex virus infection

  Summary

  Infection with herpes simplex virus type 1 (HSV-1) or HSV type 2 (HSV-2) can cause oral, genital, or ocular ulcers. Primary or recurrent HSV infections may also present at other sites with neurologic, ocular, hepatic, or respiratory complications. Worldwide, it was estimated that 67% of persons ages 0 to 49 years were infected with HSV-1 in 2012.[23]​ HSV establishes latency and periodically reactivates. Most reactivations are asymptomatic but can result in transmission of the virus. HSV-1 commonly causes oral herpes (herpes labialis) and is also associated with HSV encephalitis. HSV-2 causes genital herpes and is transmitted via sexual contact. Symptoms of oral herpes include tingling and burning followed by development of vesicular and then ulcerative lesions involving the oropharynx and perioral mucosa. Symptoms of genital herpes range from asymptomatic to tingling and burning without lesions, to recurrent genital ulcerations.[2]​ The diagnosis can be made clinically, but HSV culture or PCR should be performed on active lesions if there is a question about the diagnosis. Glycoprotein G-based type-specific serology testing is used to diagnose infection with or without lesions and distinguish between type 1 and 2. Key risk factors include HIV infection and immunosuppressive medications. 
• Genital warts

  Summary

  The most prevalent form of viral genital mucosal lesions, caused by infection with several types of human papillomavirus (HPV).[24] In Latin America, the prevalence of HPV infection is among the highest in the world.[25]​ Lesions are usually 1 to 3 mm, flesh-colored, whitish, or hyperpigmented, discrete, sessile, smooth-surfaced exophytic papillomas, or they may coalesce into larger plaques. These plaques may be extensive, with expansion into the urethra, or into the anal or vaginal canals. Key diagnostic factors include exposure to HPV through intercourse at a young age and/or increasing number of lifetime sexual partners, immunosuppression, and presence of sessile exophytic papillomas. Diagnosis is based on clinical presentation.[24]
• HIV infection

  Summary

  Caused by a retrovirus that infects and replicates in human lymphocytes and macrophages, eroding the integrity of the human immune system over a number of years. There are approximately 39 million people living with HIV globally.[26]​ Common symptoms include fevers and night sweats, loss of weight, skin rashes, oral thrush or ulceration, diarrhea, headaches, and changes in mental status or neuropsychiatric function. Key risk factors for contracting HIV infection include HIV-infected blood transfusion, intravenous drug use, homo- and heterosexual unprotected sexual intercourse, and percutaneous needle prick injury. Diagnosis is established using an initial HIV antibody or combination antibody/antigen test and confirmed using a more specific test. Patients should be clinically staged according to World Health Organization or US Centers for Disease Control and Prevention criteria.[27] [28]​
• Post-exposure HIV prophylaxis

  Summary

  Post-exposure prophylaxis (PEP) is the administration of antiretroviral therapy (ART) to HIV-negative people who may have been occupationally or sexually exposed to HIV. PEP reduces the probability of HIV transmission by 80% when taken within 72 hours following exposure, and for a full 28-day course as prescribed.​​[29] [30]​​​ The efficacy of PEP and the potential toxicities and adverse effects of the treatment need to be fully explained to the patient; counseling is an important step in patient management.
• Cervical cancer

  Summary

  A human papillomavirus (HPV)-related malignancy, preventable by HPV vaccination, and screening. Cervical cancer was the fourth most common malignancy in women worldwide in 2022, with an estimated 660,000 new cases and 350,000 deaths.[31]​ Cervical cancer screening by cytology (Pap testing) alone, Pap and HPV co-testing, or primary HPV testing may detect pre-invasive disease.​[32] ​It is very common for patients with cervical cancer to present with no symptoms, and to be identified at screening.​ Patients with advanced disease may present with abnormal vaginal bleeding, postcoital bleeding, vaginal discharge, pelvic or back pain, dyspareunia, or obstructive uropathy. Key factors include age 45 to 49 years, HPV infection, multiple sexual partners, early onset of sexual activity (younger than 18 years), and immunosuppression.
• Reactive arthritis

  Summary

  Reactive arthritis (ReA) is an inflammatory arthritis that occurs after exposure to certain gastrointestinal and genitourinary infections.[33]​ The bacteria associated with ReA are common causes of venereal disease and infectious dysentery. The most commonly implicated bacterial species are Chlamydia, Salmonella, Campylobacter, Shigella, and Yersinia species, although ReA has been described after many other bacterial infections. The classic triad of postinfectious arthritis, nongonococcal urethritis, and conjunctivitis is frequently described but found in only a minority of cases and not required for diagnosis.[33]​ There is no specific test for diagnosing ReA. Rather, a group of tests is used to confirm the suspicion in someone who has clinical symptoms suggestive of an inflammatory arthritis in the postvenereal or postdysentery period. Risk factors include male gender, HLA-B27 genotype and preceding chlamydial or GI infection.
• Sexual abuse and assault

  Summary

  Sexual violence is defined as any sexual act, attempt to obtain a sexual act, unwanted sexual comments or advances, or acts to traffic or otherwise directed against a person's sexuality using coercion, by any person regardless of their relationship to the victim, in any setting, including but not limited to home and work.[34]​ Sexual assault is common and can affect adults of any age, as well as children. Young women are most at risk, but males are also sexually violated. The diagnosis of sexual abuse and sexual assault is complex and has major ramifications; it is therefore important to follow diagnostic guidelines. In children, confirmation of certain infections (HIV, syphilis, gonorrhea, chlamydia, trichomonas) is diagnostic of sexual contact once perinatal (and percutaneous, in the case of HIV) transmission is excluded, while others (herpes simplex virus, anogenital condyloma acuminatum) are suspicious for sexual contact.[35]​ Bacterial vaginosis is inconclusive for sexual contact. In sexually active adults, it is often difficult to determine whether infections resulted from sexual assault or were pre-existing.​
• Hepatitis B

  Summary

  The most common liver infection globally, caused by the hepatitis B virus (HBV). Most people with hepatitis B are asymptomatic, although some will present with complications such as cirrhosis, hepatocellular carcinoma, or liver failure. People from endemic areas, injection drug users, and those with high-risk sexual behaviors are at an increased risk of infection. Serologic markers are essential in making the diagnosis and evaluating disease activity, including differentiating between people with acute and chronic infection and chronic asymptomatic carriers. Key risk factors include antenatal exposure, multiple sexual partners, men who have sex with men, injection drug use, family history of hepatitis B virus or hepatocellular carcinoma, incarceration, living in/travel to a highly endemic region, and household contact with an infected individual.
• Hepatitis C

  Summary

  Inflammation of the liver caused by the hepatitis C virus (HCV).[36] ​Globally, an estimated 50 million people have chronic hepatitis C, with about 1 million new infections occurring per year. Most common routes of transmission are through illicit injection drug use (sharing used needles) and transfusion of contaminated blood products. Most infections are asymptomatic; however, hepatic inflammation is often present and can lead to progressive hepatic fibrosis. Diagnostic tests for hepatitis C virus (HCV) are used to establish a clinical diagnosis, prevent infection through screening of donor blood, and make decisions regarding medical management of patients. Key risk factors include unsafe medical practices, intravenous or intranasal drug use, and history of blood transfusion or organ transplant.[37]​ 
• Evaluation of vaginal discharge

  Summary

  Vaginal discharge is one of the most common reasons for gynecologic visits; it may be physiologic or pathologic. Pathologic causes are commonly due to infection, mainly bacterial vaginosis, vulvovaginal candidiasis, and trichomoniasis. The true prevalence of this condition is uncertain because vaginitis, which encompasses the symptom vaginal discharge, is often asymptomatic, self-diagnosed, and self-treated.[38]​
• Evaluation of dyspareunia

  Summary

  Dyspareunia, or painful sexual intercourse, is a common symptom among women. It may result from various causes, including inflammatory, infectious, mucosal, and musculoskeletal conditions. One systematic review reported dyspareunia prevalence ranging from 1.3% to 45%.[39] ​Dyspareunia can be categorized as: primary (pain associated with intercourse since the onset of sexual activity), secondary (acquired over a patient's sexual lifetime); as well as superficial (painful intercourse that is localized to the introital area, due to disorders of the vulva and vestibule) or deep (often related to disorders in the pelvis).[40]
• Evaluation of dysuria

  Summary

  Discomfort, burning, or sensation of pain during micturition. Dysuria is a common condition but can be challenging to diagnose, as it is often present in conjunction with other lower urinary tract symptoms. Dysuria is a common presentation in primary care. Although urinary tract infection is the most common cause, any infectious or inflammatory condition affecting the genitourinary system may cause dysuria.