Every day, there are more than 1m new cases of curable sexually transmitted infections (STIs) among people aged 15-49 years, according to data released by the World Health Organisation. This amounts to more than 376m new cases annually of four infections – chlamydia, gonorrhoea, trichomoniasis, and syphilis.
“We’re seeing a concerning lack of progress in stopping the spread of sexually transmitted infections worldwide,” said Dr Peter Salama, executive director for universal health coverage and the life-course at WHO. “This is a wake-up call for a concerted effort to ensure everyone, everywhere can access the services they need to prevent and treat these debilitating diseases.”
The research shows that among men and women aged 15–49 years, there were 127m new cases of chlamydia in 2016, 87m of gonorrhoea, 6.3m of syphilis and 156m of trichomoniasis.
These STIs have a profound impact on the health of adults and children worldwide. If untreated, they can lead to serious and chronic health effects that include neurological and cardiovascular disease, infertility, ectopic pregnancy, stillbirths, and increased risk of HIV. They are also associated with significant levels of stigma and domestic violence. Syphilis alone caused an estimated 200,000 stillbirths and newborn deaths in 2016, making it one of the leading causes of baby loss globally.
Since the last published data for 2012, there has been no substantive decline in either the rates of new or existing infections. On average, approximately 1 in 25 people globally have at least one of these STIs, according to the latest figures, with some experiencing multiple infections at the same time.
STIs spread predominantly through unprotected sexual contact, including vaginal, anal and oral sex. Some – including chlamydia, gonorrhoea, and syphilis – can also be transmitted during pregnancy and childbirth, or, in the case of syphilis, through contact with infected blood or blood products, and injecting drug use. STIs are preventable through safe sexual practices, including correct and consistent condom use and sexual health education.
Timely and affordable testing and treatment are crucial for reducing the burden of STIs globally, alongside efforts to encourage people who are sexually active to get screened for STIs. WHO further recommends that pregnant women should be systematically screened for syphilis as well as HIV.
All bacterial STIs can be treated and cured with widely available medications. However, recent shortages in the global supply of benzathine penicillin has made it more difficult to treat syphilis. Rapidly increasing antimicrobial resistance to gonorrhoea treatments is also a growing health threat, and may lead eventually to the disease being impossible to treat.
WHO generates estimates to assess the global burden of STIs, and to help countries and health partners respond. This includes research to strengthen prevention, improve quality of care, develop point-of-care diagnostics and new treatments, and generate investment in vaccine development.
More data was available from women than men to generate these global estimates, and STI prevalence data remains sparse for men globally. WHO is seeking to improve national and global surveillance to ensure availability of reliable information on the extent of the STI burden worldwide.
The data provides the baseline for monitoring progress against the Global Health Sector Strategy on STIs 2016–2021. The strategy, adopted by the World Health Assembly in May 2016, proposed rapid scale-up of evidence-based interventions and services to end STIs as a public health concern by 2030.
Objective: To generate estimates of the prevalence and incidence of urogenital infection with chlamydia, gonorrhoea, trichomoniasis and syphilis in women and men, aged 15–49 years, in 2016.
Methods: For chlamydia, gonorrhoea and trichomoniasis, we systematically searched for studies conducted between 2009 and 2016 reporting on prevalence. We also consulted regional experts. To generate estimates, we used Bayesian meta-analysis. For syphilis, we aggregated the national estimates generated by using Spectrum-STI.
Findings: For chlamydia, gonorrhoea and/or trichomoniasis, 130 studies were eligible. For syphilis, the Spectrum-STI database contained 978 data points for the same period. The 2016 global prevalence estimates in women were: chlamydia 3.8% (95% uncertainty interval, UI: 3.3–4.5); gonorrhoea 0.9% (95% UI: 0.7–1.1); trichomoniasis 5.3% (95% UI:4.0–7.2); and syphilis 0.5% (95% UI: 0.4–0.6). In men prevalence estimates were: chlamydia 2.7% (95% UI: 1.9–3.7); gonorrhoea 0.7% (95% UI: 0.5–1.1); trichomoniasis 0.6% (95% UI: 0.4–0.9); and syphilis 0.5% (95% UI: 0.4–0.6). Total estimated incident cases were 376.4 million: 127.2 million (95% UI: 95.1–165.9 million) chlamydia cases; 86.9 million (95% UI: 58.6–123.4 million) gonorrhoea cases; 156.0 million (95% UI: 103.4–231.2 million) trichomoniasis cases; and 6.3 million (95% UI: 5.5–7.1 million) syphilis cases.
Conclusion: Global estimates of prevalence and incidence of these four curable sexually transmitted infections remain high. The study highlights the need to expand data collection efforts at country level and provides an initial baseline for monitoring progress of the World Health Organization Global Health Sector Strategy on STIs 2016–2021.
Jane Rowley, Stephen Vander Hoorn, Eline Korenromp, Nicola Low, Magnus Unemo, Laith J Abu-Raddad, R Matthew Chico, Alex Smolak, Lori Newman, Sami Gottlieb, Soe Thwin, Nathalie Brouteta, Melanie M Taylor