Overview of Sexually Transmitted Infections

J. Dennis Fortenberry

GENERAL OVERVIEW

From a clinical and public health perspective, sexually transmitted infections (STIs) are visible tracks marking the developmental trails of sexuality through adolescence into young adulthood. Sexuality itself occupies an uncomfortable, ambiguous position among the health challenges of adolescence and young adulthood—the appropriate experiential elements of healthy sexual learning balanced against the threats posed by STIs that may reverberate through the lifespan.

The key clinical considerations of adolescent and young adult (AYA) sexual health include issues of sexuality, discussions during clinical visits that identify knowledge, attitudes, and behaviors that increase or reduce risk of acquiring an STI, immunization, screening by physical examination and laboratory testing, treatment of identified infections, and counseling for partner treatment and prevention of new infections. Annual attention to these issues is recommended and some experts suggest even more frequent risk-reduction counseling and screening, particularly in AYAs with prior infections or in those involved in higher STI risk sexual behaviors.¹ STI screening provides an opportunity to discuss human immunodeficiency virus (HIV) testing and prevention.

STIs are associated with significant disease burden among AYAs.² Rates of both gonorrhea and chlamydia genital infections in the US are highest among 20- to 24-year-olds, closely followed by 15- to 19-year-olds. Chlamydia rates are about 3% among 15- to 25-year-old women, but may be 6% or more among non-Hispanic Black women. Chlamydia prevalence decreases when aggressive community-wide screening and treatment policies are implemented. Trichomonas vaginalis rates are up to 14% in young women and 3% to 5% in asymptomatic young men. Serological studies show positivity rates for herpes simplex virus type 2 (HSV-2) of up to 40% for some groups of AYAs; most do not have symptomatic infection. HSV type 1 is now a common cause of genital herpes among AYAs. Evidence for human papillomavirus (HPV) infection may be seen in up to one-third of some clinical samples. Three vaccines for some HPV types are commercially available. Clinician recommendation is an important element for acceptance of HPV vaccination by parents, adolescents, and by young adults.³ These HPV vaccines—along with hepatitis B vaccines—are associated with significant decreases in infections, transmissions to others, and adverse outcomes caused by sexually transmitted viruses.

The elevated risk for some STIs in AYAs is almost certainly multifactorial in origin, and may change as adolescents transition into young adulthood.⁴ Developmental susceptibility of the reproductive tract of young women, the substantial rates of sex partner infections, and inconsistent or incorrect condom use are potential contributors. Socioenvironmental risks such as high endemic STI rates, sexual and physical abuse, social chaos, poverty, drug trafficking and use, and inadequate health care access also contribute and may be more powerful explanations of STI risk than developmental or individual behaviors.

Diagnostic tests for many STIs, particularly gonorrhea and chlamydia, have been revolutionized by nucleic acid amplification test (NAAT) and hybrid capture (HC) techniques. NAAT and HC techniques have replaced culture diagnosis in many areas, and have the advantage of automated, high throughput systems that maintain relatively low testing costs. NAAT and HC have the added advantage of use of urine or vaginal samples, as well as traditional cervical, urethral, and anal samples.

APPROACHES TO STI DIAGNOSIS, TREATMENT, AND PREVENTION

STIs constitute a diverse set of etiologic agents most often transmitted through one or more of the between-person interactions called “sex.” Behaviors identified as “sex” are quite diverse, however, and it is important to remember that no single behavior—including penile-vaginal intercourse—is universally endorsed as “sex.”⁵ It is likely that some patients do not accurately answer clinicians’ questions about sexual activity. It is also likely, however, that many clinicians simply fail to ask at all, fail to ask the right question, or do not allow sufficient time for a response. A recent study showed that 36 seconds was the average time spent by physicians in discussing sexual issues in health maintenance visits.⁶

The various etiologic agents of STIs vary in terms of specific types of sexual contact associated with transmission, the tissue or organ typically infected, ease of diagnosis, and outcomes of treatment. The diversity of organisms and their diagnostic approaches and treatments appropriately require focused attention in the organism- or condition-specific chapters that follow. However, the relative specificity of organisms for some tissues create symptoms and signs that allow a narrower differential diagnosis and more focused diagnostic testing (Table 56.1). Several additional issues for STI diagnosis, treatment, and prevention are summarized below.

TABLE 56.1 STIs by Presenting Symptom