WHO updates fact sheet on Sexually Transmitted Infections (STIs) (28 February 2019)

The World Health Organization (WHO) has updated its fact sheet on sexually transmitted infections (STIs).

Background Information:

More than 30 different bacteria, viruses and parasites are known to be transmitted through sexual contact. Eight of these pathogens are linked to the greatest incidence of sexually transmitted disease. Of these 8 infections, 4 are currently curable:

  1. syphilis,
  2. gonorrhoea,
  3. chlamydia and
  4. trichomoniasis.

The other 4 are viral infections and are incurable:

  1. hepatitis B,
  2. herpes simplex virus (HSV or herpes),
  3. HIV, and
  4. human papillomavirus (HPV).

STIs are spread predominantly by sexual contact, including vaginal, anal and oral sex. Some STIs can also be spread through non-sexual means such as via blood or blood products. Many STIs—including chlamydia, gonorrhoea, primarily hepatitis B, HIV, and syphilis—can also be transmitted from mother to child during pregnancy and childbirth.

A person can have an STI without having obvious symptoms of disease. Common symptoms of STIs include

  • vaginal discharge,
  • urethral discharge or burning in men,
  • genital ulcers, and
  • abdominal pain.

Key Messages:

More than 1 million sexually transmitted infections (STIs) are acquired every day worldwide.

Each year, there are estimated 357 million new infections with 1 of 4 STIs:

  1. chlamydia (131 million),
  2. gonorrhoea (78 million),
  3. syphilis (5.6 million) and
  4. trichomoniasis (143 million).

More than 500 million people are living with genital HSV (herpes) infection.

At any point in time, more than 290 million women have an HPV infection.

The majority of STIs have no symptoms or only mild symptoms that may not be recognized as an STI.

STIs can have serious consequences beyond the immediate impact of the infection itself:

STIs like herpes and syphilis can increase the risk of HIV acquisition three-fold or more.

Mother-to-child transmission of STIs can result in

  • stillbirth,
  • neonatal death,
  • low-birth-weight and prematurity,
  • sepsis,
  • pneumonia,
  • neonatal conjunctivitis, and
  • congenital deformities.

Over 900 000 pregnant women were infected with syphilis resulting in approximately 350 000 adverse birth outcomes including stillbirth in 2012.

HPV infection causes 528 000 cases of cervical cancer and 266 000 cervical cancer deaths each year.

STIs such as gonorrhoea and chlamydia are major causes of pelvic inflammatory disease (PID) and infertility in women.

The only inexpensive, rapid tests currently available for STIs are for syphilis and HIV. The syphilis test is already in use in some resource-limited settings. The test is accurate, can provide results in 15 to 20 minutes, and is easy to use with minimal training.

Effective treatment is currently available for several STIs.

  • Three bacterial STIs (chlamydia, gonorrhoea and syphilis) and one parasitic STI (trichomoniasis) are generally curable with existing, effective single-dose regimens of antibiotics.
  • For herpes and HIV, the most effective medications available are antivirals that can modulate the course of the disease, though they cannot cure the disease.
  • For hepatitis B, immune system modulators (interferon) and antiviral medications can help to fight the virus and slow damage to the liver.

Drug resistance, especially for gonorrhoea, is a major threat to reducing the impact of STIs worldwide.

Low- and middle-income countries rely on identifying consistent, easily recognizable signs and symptoms to guide treatment, without the use of laboratory tests. This is called syndromic management. This approach, which often relies on clinical algorithms, allows health workers to diagnose a specific infection on the basis of observed syndromes (e.g., vaginal discharge, urethral discharge, genital ulcers, abdominal pain).

Syndromic management is simple, assures rapid, same-day treatment, and avoids expensive or unavailable diagnostic tests. However, this approach misses infections that do not demonstrate any syndromes – the majority of STIs globally.

Safe and highly effective vaccines are available for 2 STIs: hepatitis B and HPV.

Other biomedical interventions to prevent some STIs include adult male circumcision and microbicides.

  • Male circumcision reduces the risk of heterosexually acquired HIV infection in men by approximately 60% and provides some protection against other STIs, such as herpes and HPV.
  • Tenofovir gel, when used as a vaginal microbicide, has had mixed results in terms of the ability to prevent HIV acquisition, but has shown some effectiveness against HSV-2.

Counselling and behavioural interventions offer primary prevention against STIs (including HIV), as well as against unintended pregnancies. These include:

  • comprehensive sexuality education, STI and HIV pre- and post-test counselling;
  • safer sex/risk-reduction counselling, condom promotion;
  • interventions targeted at key populations, such as sex workers, men who have sex with men and people who inject drugs; and
  • education and counselling tailored to the needs of adolescents.

In addition, counselling can improve people’s ability to recognize the symptoms of STIs and increase the likelihood they will seek care or encourage a sexual partner to do so. Unfortunately, lack of public awareness, lack of training of health workers, and long-standing, widespread stigma around STIs remain barriers to greater and more effective use of these interventions.

When used correctly and consistently, condoms offer one of the most effective methods of protection against STIs, including HIV. Female condoms are effective and safe, but are not used as widely by national programmes as male condoms.

People seeking screening and treatment for STIs face numerous problems. These include limited resources, stigmatization, poor quality of services, and little or no follow-up of sexual partners.

  • In many countries, STI services are provided separately and not available in primary health care, family planning and other routine health services.
  • In many settings, services are often unable to provide screening for asymptomatic infections, lacking trained personnel, laboratory capacity and adequate supplies of appropriate medicines.
  • Marginalized populations with the highest rates of STIs—such as sex workers, men who have sex with men, people who inject drugs, prison inmates, mobile populations and adolescents—often do not have access to adequate health services.

Useful Links:

Link to the updated fact sheet:


Link to WHO’s Global Health Observatory data on STIs:



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