What are sexually transmitted infections? How are they transmitted? Sexually transmitted infections (STIs) are caused by more than 30 different bacteria, viruses and parasites and are primarily transmitted through sexual contact (including vaginal, anal and oral sex). Some sexually transmitted infections can be transmitted through sexual contact with skin-to-skin contact. The microorganisms that cause sexually transmitted infections can also be transmitted through routes other than sexual contact, such as sharing blood products and tissue transplants. Many sexually transmitted infections – including chlamydia, gonorrhea, hepatitis B, HIV, human papillomavirus, herpes simplex virus2 and syphilis – can also be passed from mother to baby during pregnancy and delivery. Sexually transmitted infections can occur without any obvious symptoms of disease. Therefore, the term “sexually transmitted infections” is broader than “sexually transmitted diseases”. Common symptoms of STIs include vaginal discharge, male urethral discharge, genital ulcers, and abdominal pain. Of the more than 30 pathogens known to be transmitted through sexual contact, eight have the highest probability of causing disease. Of these eight infections, four are currently curable: syphilis, gonorrhea, chlamydia, and trichomonas. The other four are viral infections and are not curable, but can be remitted and controlled with treatment: hepatitis B, herpes, HIV, and HPV. Scope of the problem Worldwide, sexually transmitted infections (STIs) have a profound impact on sexual and reproductive health and are among the top five categories of diseases for which adults seek health care. More than 1 million people acquire sexually transmitted infections every day. Each year, an estimated 500 million people acquire one of four sexually transmitted infections: chlamydia, gonorrhea, syphilis and trichomonas. More than 530 million people carry herpes simplex virus.2 More than 290 million women have human papillomavirus infection, one of the most common sexually transmitted infections. In addition to the direct effects of the infection itself, sexually transmitted infections can have serious consequences. Some sexually transmitted infections can triple or even increase the risk of acquiring HIV. Mother-to-child transmission of sexually transmitted infections can lead to stillbirth, neonatal death, low birth weight and preterm birth, sepsis, pneumonia, neonatal conjunctivitis and congenital malformations. Syphilis in pregnancy causes about 300,50,000 fetal and neonatal deaths per year and 21,50,000 infants are at increased risk of death caused by preterm birth, low birth weight or congenital disorders. Human papillomavirus infection causes 530,000 cases of cervical cancer and 270,000 cervical cancer deaths each year. Sexually transmitted infections such as gonorrhea and chlamydia are the leading causes of pelvic inflammatory disease, adverse pregnancy outcomes and infertility. Prevention of STIs Counseling and behavioral approaches Counseling and behavioral interventions provide primary prevention for avoiding STIs (including HIV) and unintended pregnancies. It includes: comprehensive sexuality education, pre- and post-testing counseling for STIs and HIV; counseling on safer sex/risk reduction, condom promotion; and interventions targeting key populations and vulnerable populations (e.g., adolescents, sex workers, men who have sex with men, and people who inject drugs). In addition, counseling can improve people’s ability to recognize symptoms of STIs and increase the likelihood that they will seek health care or encourage their sexual partners to seek health care. Unfortunately, lack of public awareness, lack of training for health workers, and the persistent and widespread stigma associated with STIs remain barriers to greater and more effective use of these interventions. Barrier methods When used correctly and consistently, condoms are one of the most effective ways to prevent sexually transmitted infections (including HIV). Female condoms are safe and effective, but their use is not as widely promoted in national programs as male condoms. Diagnosis of sexually transmitted infections Accurate diagnostic testing for sexually transmitted infections is widely used in high-income countries. It is particularly effective for the diagnosis of asymptomatic infections. However, in low- and middle-income countries, diagnostic testing is not widely available. When tests are available, they are often expensive and geographically inaccessible, and patients often have to wait long periods of time (or need to travel) to obtain test results, thus frustrating subsequent steps and potentially incomplete health care or treatment. The only inexpensive and rapid blood test available for sexually transmitted infections is the syphilis test. This test is already in use in some resource-limited settings. The test is accurate, provides results in 15 to 20 minutes, and is convenient to perform with minimal training. After the introduction of the rapid syphilis test, the number of pregnant women tested for syphilis has increased. However, in most low- and middle-income countries, more work is still needed to ensure that all pregnant women are tested for syphilis. Several rapid tests for other STIs are in development and will likely improve the ability to diagnose and treat STIs, especially in resource-limited settings. Treatment of Sexually Transmitted Infections Several STIs are currently amenable to effective treatment. Three bacterial STIs (chlamydia, gonorrhea, and syphilis) and one parasite-induced STI (trichomonas) are generally curable with currently effective single-agent antibiotic therapy. For herpes and HIV, the most effective drugs available are antiviral drugs that control the disease condition but do not cure it. For hepatitis B, immune system modulators (interferons) and antiviral drugs can help fight the virus and delay damage to the liver. Sexually transmitted infections, especially gonorrhea, have become rapidly resistant to antibiotics in recent years, leaving fewer treatment options available. Gonorrhea is known to show antimicrobial resistance to penicillins, sulfonamides, tetracyclines, quinolones, and macrolides, and now there is reduced susceptibility to the “last line of defense” treatment options (oral and injectable cephalosporins), making gonorrhea a multidrug-resistant organism. Antimicrobial resistance in other sexually transmitted infections, although less common, is also present, making prevention and timely treatment essential. Case management of sexually transmitted infections Low- and middle-income countries rely on sign management, which is based on the identification of groups with consistent symptoms and easily recognizable signs (syndromes) to guide treatment without the use of laboratory tests. This approach typically relies on clinical algorithms that enable health workers to diagnose a specific infection based on observed signs. Signs management is easy to perform and ensures rapid treatment on the same day, avoiding expensive or unavailable diagnostic tests. However, this approach is unable to diagnose infections without any signs, and most STIs globally are sign-free infections. Vaccines and other biomedical interventions Safe and highly effective vaccines are available for two STIs: hepatitis B and human papillomavirus. These vaccines represent a major advance in STI prevention. Hepatitis B vaccine has been incorporated into infant immunization programs in 93% of countries, and the vaccine has saved an estimated 1.3 million deaths from chronic liver disease and cancer. HPV vaccine is available as part of routine immunization programs in 45 countries, most of which are high- and middle-income countries. Most cervical cancer cases occur in low- and middle-income countries, and if 70% vaccine coverage could be achieved in these countries, the HPV vaccine could prevent more than 4 million women’s deaths in the next decade. Development of vaccines for herpes and HIV is advancing, but vaccines for both infections are not yet available. Vaccines for chlamydia, gonorrhea, syphilis, and trichomonas are still in the early stages of development. Other biomedical interventions to prevent sexually transmitted infections include adult male circumcision and microbicides. Male circumcision reduces the risk of men acquiring HIV infection through heterosexual sex by approximately 60% and provides a level of protection against other sexually transmitted infections such as herpes and human papilloma virus. Tenofovir gel, a microbicide that helps women actively avoid HIV infection, reached the “proof-of-concept” stage in clinical trials in 2010. Further clinical studies are underway to support regulatory approval of its safety and efficacy. Behavior change is complex Although much work has been done to identify simple interventions that reduce risky behaviors, behavior change remains an intricate challenge. Research has shown that there is a need to focus on carefully defined populations and to consult widely with identified target populations to involve them in the development, implementation, and evaluation of interventions. Health service linkages for screening and treatment of STIs remain weak People seeking STI screening and treatment services face multiple difficulties, including limited resources, stigma, poor quality services, and little or no follow-up with their sexual partners. In many countries, health services for STIs are provided in a stand-alone manner, with no relevant components in primary health care, family planning, and other routine health services. In many cases, screening services for asymptomatic infections are often not available due to a lack of trained personnel, laboratory capacity, and adequate supplies of appropriate drugs. Marginalized populations with the highest rates of STIs, such as sex workers, men who have sex with men, injecting drug users, prison inmates, mobile populations, and adolescents, often do not have access to adequate health services. WHO’s response WHO has developed global norms and standards for the treatment and prevention of sexually transmitted infections, strengthened surveillance and monitoring systems, including for drug-resistant gonorrhea, and led the development of a global research agenda for sexually transmitted infections. Our work is guided by Millennium Development Goals 4, 5 and 6, as well as the Global Strategy for the Prevention and Control of Sexually Transmitted Infections adopted by the World Health Assembly in 2006 and the UN Secretary-General’s Global Strategy for Women’s and Children’s Health in 2010. The UN Secretary-General’s strategy highlights the need for a comprehensive and integrated package of essential interventions, including information and services for the prevention of HIV and other sexually transmitted infections. WHO works with countries to: strengthen effective health services for STIs, including: STI case management and counseling; syphilis testing and treatment, especially for pregnant women; and hepatitis B and HPV immunization. Promote strategies to enhance the impact of STI prevention efforts, including: integrating STI services into current health systems; promoting sexual health; measuring the disease burden of STIs; and monitoring and responding to antimicrobial resistance to STIs. Support the development of new technologies for STI prevention, such as: diagnostic tests for STIs at health sites; alternative medicines for gonorrhea treatment; and STI vaccines and other biomedical interventions.