Key Facts
- Daily Infections: More than 1 million curable sexually transmitted infections (STIs) are acquired daily worldwide among individuals aged 15–49, and most are asymptomatic.
- New Infections in 2020: In 2020, there were an estimated 374 million new cases of four curable STIs: chlamydia, gonorrhoea, syphilis, and trichomoniasis.
- Syphilis in 2022: An estimated 8 million adults aged 15 to 49 were infected with syphilis in 2022.
- Herpes Prevalence: Around 520 million individuals aged 15–49 (about 13%) globally have herpes simplex virus type 2 (HSV-2), the primary cause of genital herpes.
- HPV and Cancer: Human papillomavirus (HPV) infection is linked to over 311,000 cervical cancer deaths annually.
- Pregnancy Risks: In 2022, an estimated 1.1 million pregnant women were infected with syphilis, leading to over 390,000 adverse birth outcomes.
- Impact of STIs: STIs significantly affect sexual and reproductive health, contributing to stigmatization, infertility, cancer, pregnancy complications, and heightened HIV risk.
- Antimicrobial Resistance: Drug resistance poses a significant challenge to controlling the global burden of STIs.
Overview
STIs encompass over 30 known pathogens that can be transmitted through various forms of sexual contact, including vaginal, anal, and oral sex. Some STIs can also be transmitted from mother to child during pregnancy, childbirth, and breastfeeding. Among these pathogens, eight are responsible for the highest incidence of STIs: four are curable bacterial infections (syphilis, gonorrhoea, chlamydia, and trichomoniasis), while four are viral (hepatitis B, herpes simplex virus, HIV, and human papillomavirus).
Emerging infections, such as mpox and Shigella sonnei, alongside re-emerging STIs like lymphogranuloma venereum, present new challenges for STI prevention and control. These developments highlight the increasing complexity of providing adequate health services.
Scope of the Problem
STIs represent a major public health concern globally. Each day, over 1 million curable STIs are acquired, with a staggering 374 million new infections reported in 2020 alone for chlamydia, gonorrhoea, syphilis, and trichomoniasis. Moreover, 520 million people live with genital herpes, and around 300 million women have HPV infections, which are crucial in cervical cancer development. The burden of chronic hepatitis B infection is also significant, with an estimated 254 million cases reported in 2022.
STIs have far-reaching consequences that extend beyond immediate symptoms. They can facilitate the acquisition of HIV and cause serious conditions, such as:
- Increased risks of HIV transmission related to infections like herpes and syphilis.
- Mother-to-child transmission leading to serious health complications, including stillbirth and congenital deformities.
- Cancer risks associated with HPV infection.
- A significant death toll from hepatitis B, mostly due to liver-related diseases.
- Gonorrhoea and chlamydia being leading causes of pelvic inflammatory disease and infertility in women.
Prevention of STIs
Condoms are among the most effective protection methods against STIs, including HIV, when used correctly and consistently. However, they do not protect against all STIs, particularly those causing extra-genital ulcers like syphilis or genital herpes. Therefore, condom use is recommended for all vaginal and anal sexual activities.
Vaccination campaigns have made strides in preventing viral STIs, notably hepatitis B and HPV. By the end of 2023, the HPV vaccine was integrated into the routine immunization schedules of 140 countries. To combat cervical cancer globally by 2030, achieving high vaccination rates and consistent screening and treatment for precancerous lesions is essential.
Research efforts are underway to develop vaccines for other STIs. Notably, several candidates are in clinical trials for genital herpes, and preliminary data suggest that the MenB vaccine could offer some protection against gonorrhoea.
Other biomedical interventions, including voluntary medical male circumcision and microbicides, are also being explored. Current trials are focused on pre- and post-exposure prophylaxis of STIs, particularly in light of rising antimicrobial resistance.
Diagnosis of STIs
Many STIs are asymptomatic, with symptoms often being vague or non-specific. In high-income nations, molecular technology diagnostics are commonly used to identify infections, including asymptomatic cases. Unfortunately, such methods are less accessible in low- and middle-income countries (LMICs), where testing for chlamydia and gonorrhoea can often be expensive and limited.
Conversely, affordable and rapid tests are available for syphilis and HIV. Rapid tests for syphilis and dual tests for HIV/syphilis are utilized in resource-limited settings, with ongoing development of other rapid diagnostic tools expected to improve detection and treatment in these areas.
Treatment of STIs
Effective treatments are available for several STIs:
- Curable bacterial STIs (chlamydia, gonorrhoea, syphilis) and the parasitic STI trichomoniasis can be treated with simple antibiotic regimens.
- For herpes and HIV, antiviral medications help manage disease progression, though they cannot cure the infections.
- Antivirals for hepatitis B aim to control the virus and mitigate liver damage.
However, rising antimicrobial resistance, particularly concerning gonorrhoea, severely limits treatment options. Programs like the Gonococcal AMR Surveillance Programme highlight troubling resistance trends against critical antibiotics, necessitating urgent attention.
STI Case Management
In LMICs, STI management often relies on recognizing symptoms and signs to guide treatment without laboratory testing. This syndromic management method allows health workers to use algorithms based on clinical observations—while this approach facilitates rapid treatment, it may also lead to overtreatment and missed opportunities for those with asymptomatic infections.
The WHO recommends enhancing syndromic management with laboratory testing as resources permit, allowing for more accurate diagnoses. STI screening in high-risk groups, including sex workers, men who have sex with men, and pregnant women, is crucial for effective management and prevention.
Controlling the Spread
Behavior Change is Complex
Despite extensive efforts to simplify interventions aimed at reducing risky sexual behavior, achieving behavioral change proves challenging. Increasing awareness about STI symptoms can encourage individuals to seek care but is often hindered by stigma, lack of knowledgeable healthcare providers, and public misconceptions.
Health Services for Screening and Treatment
Barriers persist for individuals seeking STI testing and treatment, including limited resources, stigmatization, and high out-of-pocket costs. Populations at the highest risk for STIs, such as sex workers and men who have sex with men, often lack access to sufficient health services. Many areas see STI services underfunded and neglected, impeding efforts to manage asymptomatic infections and overall healthcare quality.
WHO Response
The WHO follows a strategic plan to address STIs within its broader public health framework. Key initiatives include:
- Establishing global targets and norms for STI prevention, testing, and treatment.
- Supporting economic assessments and strengthening STI surveillance.
- Monitoring antimicrobial resistance trends in STIs.
- Advancing research into new diagnostic tests, vaccines, and treatments.
Efforts also focus on helping countries:
- Develop national strategic plans that foster open dialogues about STIs.
- Scale pandemic prevention measures, including condom distribution and vaccination.
- Enhance the integration of STI services into primary healthcare, ensuring accessibility and quality.
- Adopt point-of-care testing solutions.
- Advance health interventions targeted at high-risk populations.
By addressing these multifaceted challenges, stakeholders can take significant steps toward reducing the burden of STIs globally.
