Sexually Transmitted Infections

Primary reference(s)

WHO, 2024. Sexually Transmitted Infections (STIs). Fact Sheet. World Health Organization (WHO). Accessed 17 February 2025.

Annotations

Key relevant UN convention / multilateral treaty

International Health Regulations (2005), 3rd ed. (WHO, 2016a).

Drivers

More than 30 different bacteria, viruses and parasites are known to be transmitted through sexual contact, including vaginal, anal and oral sex. Some STIs can also be transmitted from mother–to-child during pregnancy, childbirth and breastfeeding (WHO, 2024).

Impacts

STIs have a profound impact on sexual and reproductive health worldwide (WHO, 2024). STIs can have serious consequences beyond the immediate impact of the infection itself: 

• STIs like herpes, gonorrhoea and syphilis can increase the risk of HIV acquisition.
• Mother-to-child transmission of STIs can result in stillbirth, neonatal death, low birthweight and prematurity, sepsis, neonatal conjunctivitis and congenital deformities.
• HPV infection causes cervical and other cancers.
• Hepatitis B resulted in just over 1 million deaths in 2022, mostly from cirrhosis and hepatocellular carcinoma.
• STIs such as gonorrhoea and chlamydia are major causes of pelvic inflammatory disease and infertility in women. 

People seeking screening and treatment for STIs face numerous problems. These include limited resources, stigmatization, poor quality of services and often out-of-pocket expenses.  Some 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 in high-burden countries for HIV – often do not have access to adequate and friendly health services. In many settings, STI services are often neglected and underfunded. These problems lead to difficulties in providing testing for asymptomatic infections, insufficient number of trained personnel, limited laboratory capacity and inadequate supplies of appropriate medicines (WHO, 2024).

Multi-hazard context

Despite ongoing efforts to identify simple interventions to reduce risky sexual behaviour, information, education, and counselling continue to play a key role. These strategies can improve people’s ability to recognise STI symptoms, increase the likelihood that they will seek care, and encourage their sexual partners to do the same. However, limited public awareness, insufficient training among health workers, and persistent stigma surrounding STIs remain major barriers to the effective use of these interventions (WHO, 2024).

Risk Management

Effective treatment is currently available for several STIs (WHO 2024): 

• Three bacterial (chlamydia, gonorrhoea and syphilis) and one parasitic STIs (trichomoniasis) are generally curable with existing 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, antivirals can help in fighting the virus and slowing down damage to the liver. 

Antimicrobial resistance (AMR) of STIs – in particular gonorrhoea – has increased rapidly in recent years and has reduced treatment options. The Gonococcal AMR Surveillance Programme (GASP) has shown high rates of resistance to many antibiotics including quinolone, azithromycin and extended-spectrum cephalosporins, a last-line treatment. AMR for other STIs, like Mycoplasma genitalium, also exist but are not systematically monitored (WHO, 2024). 

Safe and highly effective vaccines are available for 2 viral STIs: hepatitis B and HPV. These vaccines have represented major advances in STI prevention. By the end of 2023, the HPV vaccine had been introduced as part of routine immunization programmes in 140 countries, primarily high- and middle-income countries. To eliminate cervical cancer as a public health problem globally, high coverage targets for HPV vaccination, screening and treatment of precancerous lesions, and management of cancer must be reached by 2030 and maintained at this high level for decades. Research to develop vaccines against genital herpes is advanced, with several vaccine candidates in early clinical development. There is mounting evidence suggesting that the vaccine to prevent meningitis (MenB) provides some cross-protection against gonorrhoea. More research into vaccines for chlamydia, gonorrhoea, syphilis and trichomoniasis is needed (WHO, 2024). 

Antimicrobial resistance to sexually transmitted diseases, in particular gonorrhoea, has increased rapidly in recent years, making preventative approaches such as counselling and access to barrier methods an important part of effective risk management for these diseases (WHO, no date). 

WHO work is currently guided by the Global health sector strategy on HIV, Hepatitis and Sexually Transmitted Infections, 2022–2030 (WHO, 2022). Within this framework, WHO: 

• develops global targets, norms and standards for STI prevention, testing and treatment;
• supports the estimation and economic burden of STIs and the strengthening of STI surveillance;
• globally monitors AMR to gonorrhoea; and
• leads the setting of the global research agenda on STIs, including the development of diagnostic tests, vaccines and additional drugs for gonorrhoea and syphilis. 

As part of its mission, WHO supports countries to: 

• develop national strategic plans and guidelines;
• create an encouraging environment allowing individuals to discuss STIs, adopt safer sexual practices, and seek treatment;
• scale-up primary prevention (condom availability and use, etc.);
• increase integration of STI services within primary healthcare services;
• increase accessibility of people-centred quality STI care;
• facilitate adoption of point-of-care tests;
• enhance and scale-up health intervention for impact, such as hepatitis B and HPV vaccination, syphilis screening in priority populations;
• strengthen capacity to monitor STIs trends; and
• monitor and respond to AMR in gonorrhoea (WHO. 2024). 

Monitoring

WHO supports countries to conduct all-hazards strategic risk assessment in the contexts of health emergencies and disasters, which results in the development of a country risk profile. Empowered with the country risk profile, inclusive of a seasonal risk calendar, countries can anticipate potential emergencies before they occur to trigger early alerts and inform early actions (WHO, 2021).

WHO's Early Warning, Alert and Response System (EWARS) has been designed to improve disease outbreak detection in emergency settings, such as in countries in conflict or following a natural disaster. It is a simple and cost-effective way to rapidly set up a disease surveillance system. EWARS is deployed during an emergency as an adjunct to the national disease surveillance system. WHO works with Ministries of Health and health sector partners to train local health workers to use the system. After the emergency, EWARS should re-integrate back into the national system (WHO, no date).