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SEXUALLY TRANSMITTED INFECTIONS
STIs are caused by more than 30 different bacteria, viruses and parasites and are spread predominantly
by sexual contact. Of the eight pathogens known to be transmitted through sexual contact linked
to the greatest incidence of illness, four are currently curable (syphilis, gonorrhoea, chlamydia and
trichomoniasis) and four incurable (the viral pathogens hepatitis B, herpes, HIV and human papillomavirus
[HPV]), but susceptible to mitigation through treatment.
ACHIEVEMENTS
STIs are an important cause of morbidity and mortality; gonorrhoea
and chlamydia, for example, being major causes of pelvic inflammatory
disease, adverse pregnancy outcomes and infertility, while HPV
infection causes 264 000 cervical cancer deaths each year. 1 Syphilis
in pregnancy leads to 305 000 fetal and neonatal deaths every year
and leaves 215 000 infants at increased risk of dying from prematurity,
low birth weight or congenital disease. Some STIs can increase the
risk of HIV acquisition three-fold or more. Despite steady progress
in reducing the prevalence and incidence of STIs, there are still
an estimated 357 million new infections of curable STIs per year
(Table 5.3) as well as 84 000 deaths. Trichomoniasis and chlamydia
represent the bulk of curable STI cases, but gonorrhoea infection is
also significant, at an estimated 78 million new cases per year. The
burden of viral STIs is also high with an estimated 417 million cases of
herpes infection and 291 million women infected with HPV. 125,126,127 The
epidemiology of STIs is changing, with an increase in viral infections,
while other previously common infections, such as chancroid, have
nearly disappeared. 128,129
Reduced syphilis infection: Syphilis data show a decreasing trend
since 1995, while there has also been substantial progress towards
global elimination of congenital syphilis. Maternal and congenital
syphilis decreased by 33% between 2008 and 2012. 126 Cuba achieved
elimination of mother-to-child transmission of syphilis and HIV in 2015
and 13 more countries are promising candidates for elimination of
vertical syphilis transmission.
SUCCESS FACTORS
Evidence-based, affordable and cost-effective interventions: The
Global Strategy for the Prevention and Control of Sexually Transmitted
Infections: 2006–2015 has been adapted for use in all WHO regions
and is being used by the majority of countries. Most countries report
using syndromic case management for STI treatment and 88% of
reporting countries has updated national STI guidelines since 2006. In
addition, 60% of reporting countries has a national strategy in place for
elimination of mother-to-child transmission of syphilis. Nearly 90% of
countries reported offering symptomatic STI treatment for sex workers
in 2013 and 80% reported that STI services were available for men
who have sex with men. 126
Linkage to HIV prevention: Interventions for prevention of STIs and HIV
overlap to a large degree and programmes targeting key populations
for HIV are reaching those most at risk for STIs.
Advances in diagnosis and treatment: Rapid tests to diagnose syphilis
infection have become widely available, contributing to increased
coverage of syphilis screening and treatment, especially among
pregnant women. Antenatal screening for STIs increased globally
from 78% in 2008 to 84% in 2013 and syphilis seropositivity among
pregnant women decreased by nearly half over the same period, from
1.4% to 0.6%. 5 Treatment regimens for common STI syndromes have
been standardized and simplified with use of single-dose treatments
wherever possible.
Table 5.3
Global estimates of new cases of curable STIs, 2012 125
STI
Estimated new cases (millions)
Chlamydia trachomatis 130.9
Neisseria gonorrhoeae 78.3
Syphilis 5.6
Trichomonas vaginalis 142.6
Total 357.4
126 HEALTH IN 2015: FROM MDGs TO SDGs