Introduction Sexually-transmitted infections (STIs) are an important cause of acute illness, disability and death throughout the world. In this study, we used GBD 2013 systematic approach to analyze levels and trends in health loss due to STI for the years 1990 to 2013, for 188 countries, both sexes, and 20 separate age groups. We separately estimated deaths, years of life lost (YLLs), prevalence, incidence and years of life lived with disability (YLDs) for five different infections: gonorrhea (Neisseria gonorrhea), chlamydia (Chlamydia trachomatis), trichomoniasis (Trichomonas vaginalis), syphilis (Treponema pallidum), genital herpes due to herpes simplex virus 2 (HSV-2), and the residual category of “other” STI.

Methods Age- and sex-specific mortality due to all STI in ages 10 and over was estimated using cause-of-death ensemble modeling (CODEm). Syphilis deaths in ages 0 to 9 used a natural history model combining data on syphilis prevalence in pregnancy, live births, antenatal care coverage, routine antenatal syphilis testing, and excess neonatal mortality rates in those infected with syphilis. Years of life lost (YLL) were calculated by multiplying age-specific deaths with life expectancy at time of death. We estimated non-fatal STI burden consequent to acute, recurrent, and chronic infection as well as pelvic inflammatory disease (PID) and infertility. Our dataset was developed via systematic literature review, supplemented with national reports and hospital datasets. We modeled the epidemiology of each condition using DisMod-MR 2.0, a Bayesian meta-regression tool developed for GBD 201313, thereby generating age- and sex-specific prevalence and incidence estimates for each condition. Years of life lived with disability (YLD) were calculated by pairing symptomatic case numbers with corresponding disability weights (DW).

Results Global STI deaths decreased from 257,648 (95% UI: 154,732 to 396,443) in 1990 to 142,017 (87,589 to 213,920) in 2013. Most deaths were due to congenital syphilis which was the dominant driver of YLLs. Over 99% of all STI deaths occurred in developing countries, including 32.9% in eastern sub-Saharan Africa alone. Annualised rate of change (ARC) of age-standardized death rates globally was -3.0%, with 38 countries exceeding -5.0%. New cases of chlamydia, gonorrhea, trichomoniasis and genital herpes all increased between 1990 and 2013 and were amongst the top 25 most common acute conditions. North Africa and the Middle East saw the biggest percentage increase, driven mostly by population growth. Peak ages for incident infection in each STI were between 20 and 25 years and largely unchanged from 1990 to 2013. The most common acute STI in females was trichomoniasis whereas it was chlamydia in males. Genital herpes was by far the most common chronic infection in both sexes. In females, chlamydia and gonorrhea were the dominant driver of YLDs, mostly due to PID and infertility, whereas genital herpes was the biggest cause of disability due to STI in males.

Discussion Despite significant improvement in congenital syphilis mortality from 1990 to 2013, STI remain a significant cause of acute infection and disability throughout much of the world, even increasing in many locations. Surveillance and treatment programs for STI should remain a priority.