The Global Epidemiology of Syphilis in the Past Century - A Systematic Review Based on Antenatal Syphilis Prevalence.

Chris Richard Kenyon,Achilleas Tsoumanis,Kara Osbak,Pamela L C Small

doi:10.1371/journal.pntd.0004711

Abstract

BackgroundHow can we explain the uneven decline of syphilis around the world following the introduction of penicillin? In this paper we use antenatal syphilis prevalence (ASP) to investigate how syphilis prevalence varied worldwide in the past century, and what risk factors correlate with this variance.Methods1) A systematic review using PubMed and Google Scholar was conducted to identify countries with published data relating to ASP estimates from before 1952 until the present. Eleven countries were identified (Canada, Denmark, Finland, India, Japan, Norway, Singapore, South Africa, United States of America (USA), United Kingdom (UK) and Zimbabwe). The ASP epidemic curve for each population was depicted graphically. In South Africa and the USA, results are reported separately for the black and white populations. 2) National antenatal syphilis prevalence estimates for 1990 to 1999 and 2008 were taken from an Institute for Health Metrics and Evaluation database on the prevalence of syphilis in low risk populations compiled for the Global Burden of Diseases study and from a recent review paper respectively. National ASPs were depicted graphically and regional median ASPs were calculated for both time periods. 3) Linear regression was used to test for an association between ASP in 1990–1999 and 2008 and four risk factors (efficacy of syphilis screening/treatment, health expenditure, GDP per capita and circumcision prevalence). WHO world regions were included as potential explanatory variables.ResultsIn most populations, ASP dropped to under 1% before 1960. In Zimbabwe and black South Africans, ASP was high in the pre-penicillin period, dropped in the post-penicillin period, but then plateaued at around 6% until the end of the 20th century when ASP dropped to just above 1%. In black Americans, ASP declined in the post penicillin period, but plateaued at 3–5% thereafter. ASP was statistically significantly higher in sub-Saharan Africa in 1990–1999 and 2008 than in the other world regions (P < 0.001). On multivariate analysis in both time periods, ASP was only associated with residence in sub-Saharan Africa.ConclusionsFurther research is necessary to elucidate the reasons for the higher prevalence of syphilis in sub-Saharan Africa.

Highlights

Can a meaningful pattern be discerned in the large variations in syphilis rates over the last century? A first step toward answering this question is the mapping of syphilis rates across time and place followed by correlation analyses with possible explanatory variables [1]
How can we explain the uneven decline of syphilis around the world following the introduction of penicillin? In this paper we use antenatal syphilis prevalence (ASP) to investigate how syphilis prevalence varied worldwide in the past century, and what risk factors correlate with this variance
In Zimbabwe and black South Africans, ASP was high in the pre-penicillin period, dropped in the post-penicillin period, but plateaued at around 6% until the end of the 20th century when ASP dropped to just above 1%

Summary

Introduction

Can a meaningful pattern be discerned in the large variations in syphilis rates over the last century? A first step toward answering this question is the mapping of syphilis rates across time and place followed by correlation analyses with possible explanatory variables [1]. The prevalence of syphilis plummeted in a number of hyper endemic countries around the time of the AIDS epidemic in the late 1990s This decline was in part due to the widespread introduction of the syndromic approach to STI management [11] and in part due to the effect of AIDS mortality breaking up sexual networks [12,13,14,15]. We use the 1990–99 and 2008 national ASP estimates to assess if four risk factors, efficacy of syphilis screening/treatment, health expenditure, GDP per capita and circumcision prevalence, are correlated with ASP in these two time periods. In this paper we use antenatal syphilis prevalence (ASP) to investigate how syphilis prevalence varied worldwide in the past century, and what risk factors correlate with this variance.

Methods

Results

Conclusion