Syphilis: The return of a historic disease

Syphilis is a sexually transmitted disease (STD) caused by the bacterium Treponema pallidum subspecies pallidum.

There are currently 36 million people infected with syphilis worldwide, with 12 million new cases reported every year. Although most new syphilis cases occur in developing countries, syphilis has re-emerged as a health concern in a number of developed nations over the past decade.1

The course of syphilis infection has four clinical stages; the first and second stages of syphilis are highly infectious. While most people with syphilis have no obvious symptoms, the most common symptoms include herpetic lesions, bacterial infections, temporary rashes and allergies. Symptoms also tend be mild and difficult to recognize or distinguish from other dermatological conditions or symptoms caused by other STDs.

Syphilis can be transmitted during direct sexual contact, through blood transfusions and from a pregnant woman to her unborn child. People living with HIV are highly at risk, as are men who have sex with men, intravenous drug users, sex workers and their clients and pregnant women. Syphilis infection also greatly increases the likelihood of HIV transmission. A person is two to five times more likely to get HIV if exposed when syphilis sores are present.2


An increased threat for diverse groups


Although the widespread availability of penicillin in the 1940s significantly decreased the prevalence of syphilis, infection rates have begun to increase again in many countries in the last two decades, particularly among high-risk groups.3 Infection rates in Russia and China have increased dramatically since the late 1990s, and in the United States the syphilis prevalence rate has crept upward since 2000, increasing by 11 per cent between 2011 and 2012.4 Significant increases have also been noted in certain European countries, including in the Czech Republic, Denmark, Ireland, Spain, Sweden and the United Kingdom, with several countries reporting more than 30 per cent increases between 2009 and 2010.5

The new rise of syphilis is frequently associated with high-risk sexual practices among men who have sex with men (MSM). This group accounts for 75 per cent of all primary and secondary syphilis cases in the United States and prevalence is increasing.6 In other countries, syphilis prevalence among MSM is more than 15 per cent, including in Afghanistan, Argentina, Fiji, Guatemala, Jamaica, Morocco, Nicaragua and Paraguay.7

In the United States, heterosexually transmitted syphilis and congenital syphilis may also be emerging issues.8 Among men who have sex with women only, syphilis cases increased 4 percent between 2011 and 2012.9 Young people, who acquire nearly half of all new STDs in the United States, and are at a higher risk of acquiring STDs than other age groups for a combination of behavioural, biological and cultural factors, also exhibit a worrying trend. Youth aged 20 to 24 are contracting syphilis at the highest rate, with rates among men aged 20-24 increasing each consecutive year since 2002.10 In several European countries, the diagnosis of syphilis is increasingly common among teenagers 16-19 years old.11

Approximately 1.5 million pregnancies are affected by syphilis every year and congenital syphilis, which occurs when the infection is passed from a pregnant woman to her fetus, is a leading cause of stillbirth and perinatal mortality in many developing countries.12 Since congenital syphilis can be prevented, pregnant women should be tested for syphilis regularly and receive immediate treatment if necessary.


Persistent challenges


A number of existing challenges to prevention, diagnosis and treatment of STDs have exacerbated the new rise in syphilis. Asymptomatic in its early stages, syphilis can be difficult to identify and treat. Between 50 and 80 per cent of women with syphilis experience no symptoms, and are therefore unlikely to seek treatment. This increases the likelihood of onward transmission.13 In addition, the laboratory tests used to detect asymptomaticinfections are expensive and unlikely to be affordable in developing countries. They can also be difficult to perform, which may prevent high-risk individuals from getting tested.14

In general, discomfort with testing procedures, inaccessible health services and lack of accurate information may also be exacerbating the rise in syphilis prevalence, particularly in the developing world. In studies from Burkina Faso, Zimbabwe and Tanzania young people reported receiving most of their information about STDs from less dependable sources such as peers and the media. Low income youth in particular struggle to access adequate health services for a range of reasons, including inability to pay, lack of transportation, concerns about confidentiality, and in some countries, laws and policies restricting adolescent access to certain health services.15

In the developed world, the rise in syphilis prevalence among MSM, for example, is likely to have social and cultural causes beyond individual risk behaviours such as unprotected sex. MSM with lower economic status may have limited access to high quality health care, and stigma associated with homophobia and STDs can make it difficult for MSM to seek out testing and treatment.16 Throughout the world, the underlying social and cultural conditions affecting sexual risk-taking behaviours must be addressed in responses to the new rise in syphilis. In low-income settings everywhere, extra effort must be made to reach high-risk groups with better information and prevention efforts, increased testing coverage, and wider access to treatment and social services.


Fast and accurate diagnosis is crucial


When diagnosed in its early stages, syphilis can be successfully treated and cured. Left untreated, however, the disease can cause skin damage and may lead to the impairment of internal organs, including the heart and the brain. Early diagnosis facilitates early treatment, which in turn kills the syphilis bacteria and prevents further damage. Early diagnosis also reduces the risk of long-term complications and onward transmission of the disease. Health providers should routinely test high-risk individuals.



  1. World Health Organization (2012). Global incidence and prevalence of selected curable sexually transmitted infections – 2008 (Geneva: WHO).
  2. Centers for Disease Control and Prevention. Syphilis – CDC Fact Sheet.
  3. Wohrl, Stephan (2007). “Clinical update: syphilis in adults”, The Lancet 369.
  4. Centers for Disease Control and Prevention (2014). Sexually transmitted disease surveillance 2012 (Atlanta: CDC).
  5. European Center for Prevention and Disease Control (2012). Sexually transmitted infections in Europe 1990-2010 (Stockholm: ECDC).
  6. Centers for Disease Control and Prevention (2014). Reported STDs in the United States – 2012 national data for chlamydia, gonorrhea and syphilis.
  7. UNAIDS (2011). Global HIV/AIDS response – epidemic update and health sector progress towards universal access – progress report 2011.
  8. Stamm, Lola V. (2010). ‘Global challenge of antibiotic-resistant Treponema pallidum’, Antimicrobial Agents and Chemotherapy Feb 2010: 583-589.
  9. Centers for Disease Control and Prevention (2014). Sexually transmitted disease surveillance 2012 (Atlanta: CDC).
  10. Centers for Disease Control and Prevention (2012). STD surveillance 2011. Atlanta.
  11. Samkange-Zeeb, Florence N. et al (2011). ‘Awareness and knowledge of sexually transmitted diseases (STDs) among school-going adolescents in Europe: a systematic review of published literature’, BMC Public Health 11:727.
  12. Stamm, Lola V. (2010). ‘Global challenge of antibiotic-resistant Treponema pallidum’, Antimicrobial Agents and Chemotherapy Feb 2010: 583-589.
  13. United Nations Department of Economic and Social Affairs (2004). World Youth Report 2003: The global situation of young people (New York: United Nations).
  14. Dehne, Karl L. and Gabrielle Riedner (2005). Sexually Transmitted Infections among Adolescents: The need for adequate health services (Geneva: WHO and GTZ).
  15. Ibid.
  16. Centres for Disease Control and Prevention (2014). Reported STDs in the United States: 2012 National Data for Chlamydia, Gonorrhoea and Syphilis. CDC Fact Sheet (CDC).