Four curable sexually transmitted infections still affect millions worldwide

5 June 2019
Departmental news

The prevalence and incidence of four curable sexually transmitted infections (STIs)—chlamydia, gonorrhoea, trichomoniasis, and syphilis—remain high according to global estimates, with over one million new infections each day on average in 2016.

Published in the WHO Bulletin, the estimates underscore the continuing public health challenge posed by these four STIs. The 2016 estimates are similar to those published in 2012, both globally and by region, showing that STIs remain persistently widespread worldwide.

Free STIs, hepatitis and HIV testing at the Mongolian LGBT Center
Free STIs, hepatitis and HIV testing at the Mongolian LGBT Center
WHO/Yoshi Shimizu

Facts about STIs

STIs are among the most common communicable diseases and affect the health and lives of women, men, and babies worldwide. People who get STIs also face stigma, stereotyping, and shame and are vulnerable to gender-based violence. 

More than 30 different bacteria, viruses and parasites are known to be transmitted through vaginal, anal and oral sex, while some can also be spread through blood or blood products. Many STIs, including chlamydia, gonorrhoea, hepatitis B, herpes, HIV and syphilis, can also be transmitted from mother-to-child during pregnancy and childbirth.

STIs can cause an inflammation of the cervix, urethra, and vagina as well as genital ulceration. Chlamydia and gonorrhoea also cause rectal and pharyngeal infections and complications such as pelvic inflammatory disease, ectopic pregnancy, infertility, and chronic pelvic pain. Syphilis causes neurological and cardiovascular disease in adults, and stillbirth, neonatal death, premature delivery or severe disability in babies. All four of the STIs presented in these updated global estimates (chlamydia, gonorrhoea, syphilis and trichomoniasis) are also associated with an increased risk of acquiring and transmitting HIV.


Women and children queue to enter a free medical clinic.
Women and children queue to enter a free medical clinic treating various diseases including STIs, Somalia. 

Globally in 2016, the four infections (chlamydia, gonorrhoea, syphilis and trichomoniasis) accounted for 376.4 million new infections in 15–49-year old men and women for that year 

The African Region recorded the highest prevalence for chlamydia in men, trichomoniasis in women, and gonorrhoea and syphilis in women and men. The Region of the Americas had the highest prevalence for chlamydia in women and for trichomoniasis in men.

Compared to WHO’s previously published estimates for 2012, prevalence of these infections remained comparably high.  

The prevalence of all four STIs, in both women and men were highest in the Western Pacific Region, specifically in Oceania, which includes countries of the South Pacific (Figures below).

Chart 1
Prevalence of 4 curable STIs among Women by SDG region, 2016
Chart 2
Prevalence of 4 curable STIs among Men by SDG region, 2016


Image of table

Comparison of 2012 and 2016 WHO regional prevalence estimates of chlamydia, gonorrhoea, trichomoniasis and syphilis

Next steps

WHO periodically generates estimates of these four curable STIs to gauge the global burden of these infections and to provide evidence for programme improvement, monitoring, and evaluation.

These global and regional estimates provide the baseline for monitoring the progress of 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. These estimates indicate that current interventions have not resulted in a decline in these infections since the prior estimation year of 2012.

The estimates also have implications for STI programming and research. There is a clear need to improve the quantity and quality of STI prevalence and incidence studies in representative samples of the general population, for both women and men.

National-level STI prevalence and incidence data play an important role in designing and evaluating STI programmes and interventions. Moreover, prevalence and incidence estimates provide crucial data for advocating for funding to support STI programmes, and promoting research and development activities to improve point-of-care diagnostics, new therapeutics, vaccines, and microbicides. The global threat of antimicrobial resistance, especially for gonorrhoea, further highlights the importance of investing in monitoring STI incidence.