Sexually Transmitted Infections

Infectious Agent

More than two dozen bacterial, viral, and parasitic pathogens can cause sexually transmitted infections (STIs).


This chapter focuses on infections transmitted from person to person during sexual activity with genital, anal, or oral mucosal contact.


STIs are among the most common infectious diseases reported worldwide. There were an estimated 20 million new cases of sexually transmitted infections in the United States in 2016 and 357 million cases globally in 2012.

Casual sex during travel is common (20% prevalence in a systematic review), and some people travel for sex tourism (see Chapter 9, Sex & Travel). Sex partners abroad may include male or female commercial sex workers with elevated STI prevalence. Documented risk factors for STI/HIV acquisition among travelers to low- and middle-income countries include male gender, men who have sex with men (MSM), single marital status, and longer duration of stay. Providers caring for returning travelers should know where to find up-to-date information about global epidemiology and antimicrobial resistance patterns of STI from national (CDC, and international public health authorities (World Health Organization [WHO],

The epidemiology and clinical manifestations of common STIs are shown in Table 11-6. Returning travelers should be asked about sexual activity during their trip, with specific questions about region of travel, sexual partners, sites of sexual exposure, and condom use. Assessing risk in MSM is important because they have elevated rates of certain infections (syphilis, chlamydia, gonorrhea, and lymphogranuloma venereum). Screen travelers seeking an evaluation for STI or with evidence of STI for HIV infection. Provide anyone with HIV infection linkage to HIV care and treatment services if they are not already receiving care.

Clinical Presentation

Returning travelers should be assessed for chlamydia, gonorrhea, and syphilis, since many curable bacterial STIs are asymptomatic. Advise any traveler with sexual exposure who develops STI symptoms (vaginal, urethral, or rectal discharge, an unexplained rash or genital lesion, or genital or pelvic pain) to abstain from sex and seek prompt medical evaluation. Human papillomavirus (HPV) infection is commonly acquired within 2 years of sexual debut and usually clears spontaneously. Although most STIs involve the genital tract, some also cause disseminated disease (such as syphilis and herpes). Consider STI in returning travelers since infection can result in serious and long-term complications, including pelvic inflammatory disease, infertility, adverse birth outcomes, cervical cancer, anal cancer, and an increased risk of HIV acquisition and transmission.

Table 11-6. Epidemiology and clinical manifestations of common STIs

STI (Cause)

Geographic Location

Typical Clinical Presentation (but often asymptomatic)

Incubation Period (days)


First-Line Therapy



(Haemophilus ducreyi )

Regional in Africa, Asia, Caribbean

Irregular, painful genital ulcer; tender, suppurative inguinal lymphadenopathy


Culture with specialized media

Azithromycin 1 g PO once OR

Ceftriaxone 250 mg IM once


(Chlamydia trachomatis )


Cervicitis, urethritis



Azithromycin 1 g PO once OR

Doxycycline 100 mg PO bid x 7 days


(Neisseria gonorrhoeae )


Cervicitis, urethritis



Ceftriaxone 250 mg IM once AND

Azithromycin 1 g PO once

Granuloma inguinale

or donovanosis

(Klebsiella granulomatis )

Southern Africa, India, Papua New Guinea, Australia

Extensive genital ulcerations with granulation and easy bleeding; tender lymphadenopathy

4–28 days


donovan bodies in macrophages

Azithromycin 1 g PO weekly until resolution

Lymphogranuloma venereum

(Chlamydia trachomatis serovar L1-3)


Self-limited ulcer; tender inguinal lymphadenopathy, proctocolitis

3–30 days

NAAT, serology

Doxycycline 100 mg PO bid x 21 days


(Treponema pallidum )


Primary: painless genital ulcer, regional lymphadenopathy; secondary: maculopapular skin rash

10–90 days

Darkfield microscopy (primary infection), serology

Benzathine penicillin G

2.4 MU IM (once for primary, secondary, and early latent infection),

2.4 MU IM once weekly x 3 weeks for late latent infection or latent syphilis of unknown duration


Hepatitis A virus


Malaise, fatigue, anorexia, jaundice

28 days


Supportive care

Hepatitis B virus


Malaise, fatigue, anorexia, jaundice

60–150 days


Several options, consult with expert

Hepatitis C virus


Malaise, fatigue, anorexia, jaundice

15–50 days


Several options, consult with expert

Herpes simplex virus (HSV)


≥1 painful genital ulcers

2–7 days

Culture or PCR

Acyclovir 400 mg PO tid x 7–10 days OR

valacyclovir 1 g PO bid x 7–10 days OR

famciclovir 250 mg PO tid x 7–10 days

Human papillomavirus



14–240 days

Clinical or pathologic

Topical therapy or removal of lesion

Zika virus


Fever, rash, joint pain, conjunctivitis

3–14 days

Serology or PCR

Supportive care



(Trichomonas vaginalis )


Vaginal discharge and itching

5–28 days


Metronidazole 2 g PO once OR

tinidazole 2 g PO once

Metronidazole 500 mg bid x 7 days in women with HIV infection

Abbreviations: STI, sexually transmitted infection; PO, orally; IM, intramuscularly; NAAT, nucleic acid amplification testing; bid, twice daily; tid, 3 times daily.


Base STI evaluation, management, and follow-up on the most recent national and international guidelines from CDC and WHO. In the United States, CDC guidelines are preferred since WHO follows a syndromic approach to STI management given limited availability of diagnostic testing in many countries. Treatment failure is a possibility if an infection does not respond, which is particularly relevant in a traveler with persistent gonococcal infection given the global spread of multidrug-resistant Neisseria gonorrhoeae .


Prevention and control of STIs is based on accurate risk assessment, education, counseling, early identification of asymptomatic infection, and effective treatment of travelers and their sex partners. Pretravel advice should include specific messages with strategies to avoid acquiring or transmitting STIs. Abstinence or mutual monogamy with an uninfected partner is the most reliable way to avoid acquiring and transmitting STIs.

For people whose sexual behaviors place them at risk for STIs, correct and consistent use of the male latex condom can reduce the risk of HIV infection and other STIs, including chlamydia, gonorrhea, and trichomoniasis. Preventing lower genital tract infections might reduce the risk of pelvic inflammatory disease in women. Correct and consistent use of male latex condoms also reduces the risk of HPV infection, genital herpes, syphilis, and chancroid, although data are limited. Only water-based lubricants, such as K-Y Jelly, should be used with latex condoms because oil-based lubricants (such as petroleum jelly, shortening, mineral oil, or massage oil) can weaken latex condoms. Spermicides containing nonoxynol-9 are not recommended for STI/HIV prevention. Contraceptive methods that are not mechanical barriers do not protect against HIV or other STIs.

Prompt evaluation of sex partners is necessary to prevent reinfection and disrupt STI transmission. Preexposure vaccination is among the most effective methods for preventing certain STIs. HPV vaccines are available and licensed for girls and boys to prevent transmission. Consider all travelers as candidates for hepatitis A and hepatitis B vaccines, as these infections can be sexually transmitted. Hepatitis B vaccine is recommended for all people being evaluated or treated for an STI. Hepatitis A and hepatitis B vaccines are also recommended for MSM. Travelers at risk of acquiring HIV infection may benefit from preexposure prophylaxis (see and Chapter 4, HIV).

CDC website:


  1. Crawford G, Lobo R, Brown G, Macri C, Smith H, Maycock B. HIV, other blood-borne viruses and sexually transmitted infections amongst expatriates and travellers to low- and middle-income countries: a systematic review. Int J Environ Res Public Health. 2016;13(12).  [PMID:27999275]
  2. Meites E, Kempe A, Markowitz LE. Use of a 2-dose schedule for human papillomavirus vaccination—updated recommendations of the Advisory Committee on Immunization Practices. MMWR Morb Mortal Wkly Rep. 2016;65(49):1405–8.  [PMID:27977643]
  3. Newman L, Rowley J, Vander Hoorn S, Wijesooriya NS, Unemo M, Low N, et al. Global estimates of the prevalence and incidence of four curable sexually transmitted infections in 2012 based on systematic review and global reporting. PLoS One. 2015;10(12):e0143304.  [PMID:26646541]
  4. Vivancos R, Abubakar I, Hunter PR. Foreign travel, casual sex, and sexually transmitted infections: systematic review and meta-analysis. Int J Infect Dis. 2010;14(10):e842–51.  [PMID:20580587]
  5. Weston EJ, Wi T, Papp J. Strengthening global surveillance for antimicrobial drug-resistant Neisseria gonorrhoeae through the Enhanced Gonococcal Antimicrobial Surveillance Program. Emerg Infect Dis. 2017;23(13).  [PMID:29155673]
  6. Workowski KA, Bolan GA. Sexually transmitted diseases treatment guidelines, 2015. MMWR Recomm Rep. 2015;64(RR-03):1–137.  [PMID:26042815]


Jodie Dionne-Odom, Kimberly Workowski