Syphilis is a bacterial infection caused by Treponema pallidum that results in substantial morbidity and mortality. Syphilis is a sexually transmitted infection (STI) usually spread through contact with infectious sores on the genitals, anus, rectum, lips or mouth, via blood transfusion, or through mother-to-child transmission during pregnancy. Correct and consistent use of condoms significantly decreases the risk of infection. Mother-to-child transmission of syphilis (congenital syphilis) is preventable and can be achieved through early screening and treatment. Syphilis diagnosis is usually based on medical history, physical examination, and laboratory testing. Uncomplicated syphilis can be easily cured with antibiotics, however if left untreated, the disease last for years and cause serious health problems.

WHO estimates that 5.6 million new cases of syphilis occurred among adolescents and adults aged 15–49 years worldwide in 2012 with a global incidence rate of 1.5 cases per 1000 females and 1.5 per 1000 males. The estimated 18 million prevalent cases of syphilis in 2012 translates to a global prevalence of 0.5% among females and 0.5% among males aged 15–49 years.

Key facts

  • In 2012, there were 471 000 new cases of syphilis among females, and 466 000 new cases among males in the Region of the Americas
  • In 2012, there were around 1 million existing cases of syphilis among females, and 992 000 existing cases among males in the Region
  • According to 37 reporting countries in the Region, there were an estimated 22 800 cases of MTCT of syphilis in 2015. Approximately 50% of pregnant women with untreated syphilis will transmit the infection to their unborn child
  • Key populations are disproportionally affected, and continue to exhibit a high burden of syphilis, which ranges from 1% to 27% in the case of gay men and other men who have sex with men (MSM), and from 0.5% to 14% in female sex workers
  • 35% of countries in the Region do not test for syphilis when testing for HIV among key populations
  • Untreated syphilis increases the risk of transmitting or acquiring HIV by two or three times in some populations

PAHO/WHO response

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