CHAPTER 60

Sexually Transmitted Infections

Many teenagers in the United States have their first sexual experience before they graduate from high school. In the 2017 national Youth Risk Behavior Surveillance System conducted by the Centers for Disease Control and Prevention (CDC), 40% of all students in high school reported having had sexual intercourse, with 3.4% of students nationwide reporting sexual intercourse for the first time before age 13 years. More important, nearly 12% of boys and 8% of girls in grades 9 to 12 reported having had 4 or more sexual partners during their life. The consequences of sexual activity in adolescents include increased rates of bacterial and viral sexually transmitted infections (STIs), unintended pregnancy, and the possible acquisition of long-term infections (eg, HIV) in the 15- to 24-year age group. Early detection and effective management of these infections, particularly HIV, can greatly enhance the teenager’s current health and overall lifespan and reduce the risk of transmitting HIV to others. Because of the complex nature of these consequences, the physician must be skilled in and comfortable obtaining a complete sexual history in the adolescent patient and in diagnosing and managing common STIs and must refer individuals with more complicated infections to the appropriate subspecialists.

Increasing levels of risk-taking behaviors and sexual activity in adolescence directly affect STI trends in that patient population. Other influential factors include multiple sex partners, whether sequential or concurrent; inconsistent and incorrect use of condoms; unprotected sex; experimentation with drugs, including alcohol, which results in poor judgment concerning sexual activity; mental health issues; poor adherence to antibiotic regimens; and biologic factors, such as young age at onset of menarche and the presence of cervical ectopy in adolescent females. The feeling of invulnerability and the desire for autonomy that occur commonly during adolescence make most sexual encounters spontaneous rather than pre-meditated. As a result, preventive measures are forgotten, ignored, or overlooked by individuals of this age group, and the short- and long-term consequences of their actions are seldom considered. Other factors that influence STI trends are related to societal norms. Traditionally, unlike in other industrialized countries, educational materials and STI services have not been readily available to adolescents in some areas of the United States. Many teenagers also have difficulty accessing comprehensive health care in their communities and are concerned about confidentiality when obtaining medical services for sensitive issues. Additionally, the depiction of casual sexual relationships in the media, music videos, and motion pictures may contribute to the glamorization of sex. Advances in technology via unlimited internet access also give teenagers the opportunity to communicate with peers who were previously unreachable and to access health information that is unfiltered and may be misleading.

Epidemiology

The overall prevalence of STIs in adolescents is difficult to estimate because not all STIs are reportable, many infections are asymptomatic, and collected data may not include specific subsets of the population. It has been estimated, however, that more than 50% of all new STIs diagnosed annually in the United States occur among teenagers and young adults aged 15 to 24 years. After human papillomavirus (HPV), Chlamydia trachomatis is the second most common STI in the United States. Chlamydia trachomatis remains the most common cause of cervicitis and urethritis in adolescents, with age-specific rates highest among girls and young women 15 to 24 years of age and young men 20 to 24 years of age. Additionally, studies have shown that certain adolescent subpopulations are at increased risk for chlamydial infection, such as homeless and incarcerated youth, socioeconomically disadvantaged youth, ethnic minority youth, teenagers attending family planning clinics, and pregnant adolescents. Complications of unmanaged chlamydial cervicitis occur in 10% to 15% of cases and include pelvic inflammatory disease (PID), ectopic pregnancy, chronic pelvic pain, and infertility. Epididymitis, a result of urethral infection, occurs in 1% to 3% of infected males. Other conditions that may occur in males engaging in receptive intercourse include proctitis, proctocolitis, and reactive arthritis (formerly known as Reiter syndrome).

In 2017, the CDC reported gonorrhea rates to be highest among adolescents and young adults compared with the general population, particularly among teenage girls and young women. The highest rates of gonorrhea reportedly occur in adolescent females, young men in their early 20s, young ethnic minority adults living in the inner city, incarcerated youth, men who have sex with men, and commercial sex workers. Injection drug use, exposure to commercial sex workers, and numerous sexual contacts also contribute to the risk of infection. The prevalence of gonorrhea in 15- to 19-year-old girls and young women was 557 per 100,000 population. Boys and young men 15 to 19 years of age had the second highest rates of gonorrhea (323 per 100,000) compared with men age 20 to 24 years, who had even higher rates of gonorrhea (705 per 100,000). Of the more than 1 million cases of PID reported annually in the United States, approximately 20% occur in sexually active adolescents. The risk of developing PID is increased several fold in this age group compared with adult women for several reasons: failure to use condoms consistently, multiple new partners within the previous 12 months, and a history of other STIs. Additionally, according to the National Survey of Family Growth conducted by the CDC, girls who initiated vaginal intercourse at younger than 15 years had the highest prevalence of PID. Complications of PID, such as tubo-ovarian abscess (TOA) formation, are more likely to occur in adolescents as a result of late presentation, delayed diagnosis, difficulty accessing health care, and nonadherence with prescribed treatment regimens.

Although the rate of primary and secondary syphilis declined from 1990 to 2000, the number of cases has since been increasing at epidemic proportions, primarily among young men of color who have sex with men. During 2005, the incidence of syphilis was highest among women in the 20- to 24-year-old age group and among men in their mid-30s. In 2017, however, young men age 20 to 24 years had the highest rates of syphilis. Studies have shown that people with syphilis, as well as other STIs that cause genital ulcers, also are at increased risk for HIV acquisition.

Human papillomavirus is the most common STI in the United States, with the highest infection rates among adolescents and young adults. Recent studies report a prevalence in sexually active adolescents ranging from 30% to 60%, with one-half of new infections occurring in individuals 15 to 24 years of age. The prevalence of HPV in adolescents varies widely for 2 reasons: infection with HPV is often latent and generally regresses spontaneously, particularly in young adolescents, and HPV is not a reportable condition. Behavioral and biological risk factors for HPV infection have been identified and include early age of sexual initiation, unprotected intercourse with multiple sexual partners, the partner’s number of sexual partners, a lack of consistent condom use, and a history of another STI, such as genital herpes, which may facilitate HPV acquisition by compromising mucosal integrity. Cigarette use also increases the risk of infection and HPV-related disease, as does an altered immune system.

Infection with herpes simplex virus (HSV-1 and HSV-2) is underestimated and is the most common cause of genital ulcerative disease in the United States. Most primary episodes in adolescent females and young men who have sex with men are caused by HSV-1 and recurrent infections by HSV-2.

As of 2016, 21% of all new HIV diagnoses in the United States were among youth. According to the CDC, most of those new diagnoses occurred among young gay and bisexual men, particularly young black/African American and Hispanic/Latino gay and bisexual men. Because the time from acute HIV infection to immunosuppression is, on average, 10 years for untreated adolescents, estimates of asymptomatic or early HIV infection often are based on reported cases of AIDS in young adults in their third decade. Most of these individuals are infected through sexual contact or injection drug use. Teenage subpopulations who are at particularly high risk for acquiring HIV are youth who have male-to-male sexual contact; are transgender; are experiencing homelessness or who have run away; are users of injection drugs; are incarcerated; are in the foster care system; or have been sexually or physically abused. Of note, research has shown that young gay men who have sex with older partners are at increased risk for HIV infection because the older partner is more likely to have had more sexual partners and therefore has an increased likelihood of being infected with HIV.

Clinical Presentation

The adolescent with an STI may consult his, her, or their physician with specific complaints related to the genitourinary system, such as painful urination or vaginal discharge. The adolescent also may report more generalized complaints, such as fever, rash, and malaise, especially in cases of primary HSV-1 and HSV-2 infection or during the viremic phase of HIV acquisition (Box 60.1). Additionally, some teenagers use a vague complaint as an opportunity to visit their primary care physician with the hope that the physician will inquire about sexual behaviors. The likelihood that the adolescent will disclose his, her, or their true concern about an undiagnosed infection is greatly increased if the physician appears genuinely interested and nonjudgmental.

Pathophysiology

Several biologic factors contribute to the increased prevalence of STIs in adolescents, particularly in females. At the onset of puberty, the columnar epithelial cells in the vagina transform to squamous epithelium, while columnar cells at the cervix persist (Figure 60.1). With increasing age, the squamocolumnar junction recedes into the endocervix. In adolescent females, however, this junction, referred to as cervical ectopy, often is located at the vaginal portion of the cervix and is relatively exposed, which places these individuals at particular risk for gonococcal and chlamydial infections. The infectious organisms preferentially attach to cervical columnar cells and infect them. The use of oral contraceptives prolongs this immature histologic state.

The cytologic changes observed in cervical cells of adolescents with HPV infection are also believed to be age-related. The immature cervical metaplastic or columnar cells seem to be more vulnerable to infection and neoplastic changes. Additionally, exposure to other cofactors (eg, tobacco use, multiple episodes of new HPV infection) is likely to promote the development of squamous intraepithelial neoplasia and cervical carcinoma. Not all young women exposed to HPV develop lesions or progress to squamous intraepithelial neoplasia, however, and most do not remain positive for HPV throughout their lifetime.

Figure 60.1. Development of the cervical squamocolumnar (S-C) junction, from puberty to adulthood.

The presence of genital ulcers has been shown to facilitate the transmission and acquisition of HIV. Such ulcers provide a point of entry past denuded epithelium. Additionally, it is hypothesized that many activated lymphocytes and macrophages are located at the base of the ulcer and are therefore susceptible to infection by HIV.

Pelvic inflammatory disease usually manifests from an ascending mixed polymicrobial infection, often related to an untreated STI of the cervix and vagina. The infection spreads contiguously upward to the upper genital tract, resulting in inflammation involving the endometrium, fallopian tubes, and/or ovaries. The most common causal organisms, which account for more than one-half of the cases of PID in most series, are C trachomatis and Neisseria gonorrhoeae. Other organisms include Escherichia coli, other enteric flora, and microbes implicated in bacterial vaginosis, such as Mycoplasma hominis, Mycoplasma genitalium, Ureaplasma urealyticum , Bacteroides species, and anaerobic cocci. Viruses such as HIV and HSV-1 and HSV-2 can facilitate the process of this ascending infection by disrupting normal immunologic barriers to infection, such as altering the vaginal pH and flora and the cervical mucus barrier.

Differential Diagnosis

Most patients with STIs present with 1 of 5 clinical syndromes: urethritis/cervicitis, epididymitis, PID, genital ulcer disease, or genital warts, all of which are easily diagnosed with the appropriate diagnostic studies (Box 60.2). Other conditions that mimic STIs must be considered, however, particularly in certain cases in which the adolescent denies sexual activity or in which the disorder does not respond to routine medical management. These disorders include mucocutaneous ulcers associated with systemic lupus erythematosus and Behçet syndrome. Often, systemic disorders such as these can be ruled out based on the history, although a minimal workup may be necessary. Benign oral lesions, such as aphthous ulcers, also can be confused with herpetic ulcers. When evaluating an adolescent female with acute lower abdominal pain, it is necessary to rule out surgical conditions such as appendicitis, ovarian torsion, and ectopic pregnancy. In the sexually active male with testicular pain, testicular torsion must be cautiously considered and thoroughly evaluated before a diagnosis of acute epididymitis is made.

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