Sexually Transmitted Diseases

Infectious Agent

Sexually transmitted diseases (STDs) are the infections and resulting clinical syndromes caused by approximately 30 infectious organisms.


Sexual activity is the predominant mode of transmission, through genital, anal, or oral mucosal contact.


STDs are among the most common infectious diseases and can be caused by bacterial, viral, and parasitic pathogens. Annually, an estimated 19.7 million sexually transmitted infections occur in the United States alone. Worldwide, an estimated 498 million cases of chlamydia, gonorrhea, syphilis, and trichomoniasis occur each year. Some STDs are more prevalent in developing countries (chancroid, lymphogranuloma venereum [LGV], granuloma inguinale [donovanosis]) or in specific regions (gonorrhea with treatment failure and decreased susceptibility to cephalosporins in Asia) and may be imported into other countries by travelers returning from such locales. Infection with multiple STDs is common. Additionally, infection with an STD can facilitate the sexual transmission of HIV. Casual sexual relationships occur frequently during travel to foreign countries. In a systematic review published in 2010, the pooled prevalence of travel-associated casual sex among foreign travelers was 20.4%. In addition, commercial sex in various destinations, such as Southeast Asia, attracts many foreign travelers. Commercial sex workers in some regions have high rates of STDs, including HIV, and travelers who have sex with them risk acquiring these infections.

Knowledge of the clinical presentation, frequency of infection, and antimicrobial resistance patterns is needed to manage STDs that occur in travelers. Assessing risk for men who have sex with men is important because of the recent increased rates of infectious syphilis, gonorrhea with treatment failure and decreased susceptibility to cephalosporins, and LGV in various geographic locations.

Clinical Presentation

Many infections, such as chlamydia and gonorrhea, may be asymptomatic, so screening for these infections and serologic testing for syphilis should be encouraged among travelers who report high-risk behaviors. Any traveler with sexual exposure who develops vaginal, urethral, or rectal discharge, an unexplained rash or genital lesion, or genital or pelvic pain should be advised to cease sexual activity and promptly seek medical evaluation.

Some systemic infections are acquired through sexual transmission (such as hepatitis A, hepatitis B, hepatitis C, HIV, syphilis, Zika infection). Human papillomavirus (HPV) infection is usually subclinical and asymptomatic and most often clears spontaneously within 2 years. However, persistent HPV infection can lead to genital warts, cervical and other anogenital cancers, and oropharyngeal cancer. Because many travelers do not volunteer a history of sexual contact during travel, clinicians should inquire about sexual exposures when caring for returned travelers.


Genital ulcer evaluation should include a serologic test for syphilis and a culture or PCR test for genital herpes. If exposure occurred in areas where chancroid is more common (Africa, Asia, and Latin America), a test for Haemophilus ducreyi should also be performed. Lymphadenopathy can accompany genital ulceration with chancroid infections, as well as with LGV and donovanosis. If painful perianal ulcers are present or mucosal ulcers are detected on anoscopy, presumptive therapy should include a regimen for anogenital herpes. LGV should be suspected in a traveler with tender unilateral inguinal or femoral lymphadenopathy or proctocolitis. Presumptive treatment for LGV should be considered for men who have sex with men and who have proctitis and perianal or mucosal ulcers, after obtaining specific testing for Chlamydia trachomatis (culture, direct immunofluorescence, or nucleic acid testing) from relevant specimens (genital lesions, rectal, or lymph node). Of note, for patients presenting with proctitis, C. trachomatis nucleic acid amplification testing of a rectal specimen is recommended. While a positive result is not a definitive diagnosis of LGV, the results might aid in the presumptive clinical diagnosis of LGV proctitis. Donovanosis is endemic in India, Papua New Guinea, central Australia, and southern Africa and is diagnosed with a crush tissue preparation from the lesion.

Testing specimens from the anatomic site of exposure with nucleic acid amplification tests can detect C. trachomatis and Neisseria gonorrhoeae . Culture and antibiotic susceptibility testing should be considered when gonorrhea is suspected, because of geographic differences in antimicrobial susceptibility. Various diagnostic methods are available to identify the cause of an abnormal vaginal discharge, including microscopic evaluation and pH testing of vaginal secretions, DNA probe-based testing, nucleic acid amplification testing, and culture.

Diagnosis of anogenital warts is made by visual inspection, with confirmation by biopsy if clinically indicated.

Anyone who seeks evaluation for STDs, or is diagnosed with an STD, should be screened for HIV infection. People seeking STD care known to be HIV-infected should be provided linkage to HIV care and treatment services.


Evaluation, management, and follow-up of STDs should be based on standard guidelines (CDC and the World Health Organization). The prevalence of antimicrobial resistance in different areas should be considered when selecting treatment regimens. Early detection and treatment are important, as many STDs are asymptomatic. STDs can often result in serious and long-term complications, including pelvic inflammatory disease, infertility, stillbirths and neonatal infections, anogenital and other cancers, and an increased risk for HIV acquisition and transmission.


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

For people whose sexual behaviors place them at risk for STDs, correct and consistent use of the male latex condom can reduce the risk of HIV infection and other STDs, 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 or glycerin) 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 STD/HIV prevention, as nonoxynol-9 may disrupt genital or rectal epithelium and has been associated with an increased risk of HIV transmission. Contraceptive methods that are not mechanical barriers do not protect against HIV or other STDs.

Prompt evaluation of sexual partners is necessary to prevent reinfection and disrupt transmission of many STDs. Preexposure vaccination is among the most effective methods for preventing some STDs. Two HPV vaccines are available and licensed for girls and women aged 9–26 years to prevent cervical precancers and cancers: the quadrivalent HPV and the bivalent HPV vaccine. The quadrivalent vaccine also prevents genital warts and is recommended for boys and men aged 9–26 years as well as girls and women. All travelers should be considered candidates for both 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 STD. In addition, hepatitis A and hepatitis B vaccines are recommended for men who have sex with men and injection drug users. Travelers, particularly those at high risk for acquiring HIV infection, may consider discussing preexposure prophylaxis with their health care providers (see and HIV section in this chapter).

CDC website:


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Emily J. Weston, Kimberly Workowski