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Department of Evolutionary Biology and Environmental Studies

Population Genomics of Syphilis Epidemics

The re-emergence of an old epidemic

Prior to HIV, syphilis was the most devastating sexually transmitted disease in human history, responsible for one of the worst global epidemics. It attained notoriety in the epidemic that raged throughout Europe in the 16th century,  when soldiers returning from the war over Naples spread the infection throughout the continent. Syphilis continued to be a damaging and uncurable disease unitl the mid-20th century, when usage of antibiotics and health campaigns finally allowed a dramatic reduction of its incidence in the developed world.

Syphilis is a multi-stage bacterial infection that results from skin to skin contact, generally through sexual encounters. In 1905 Fritz Schaudinn and Erich Hoffmann identified the causative agent as Treponema pallidum pallidum, a bacterium of the spirochete family. This helical-shaped bacterium uses a corkscrew movement to progressively invade the different tissues of the body in various stages. Untreated, it can cause stillbirths and abortions, and can also lead to severe cardiological and neurological damage.

While syphilis is often viewed as a disease of the past, it is currently experiencing a dramatic global come back . In numerous developed nations the incidence of syphilis has been steadily increasing. Intriguingly, Switzerland has one of the highest rates of reported cases among western European nations. The reasons for this re-emergence are not yet fully understood.

The need for molecular and evolutionary studies

One major limitation in our understanding of syphilis infections stems from the paucity of molecular and evolutionary investigations. Such studies are useful because they shed light on the diversity and distribution of strains around the world and help us understand transmission networks. Molecular studies have been hindered by the challenges of working with a difficult bacterium such as Treponema pallidum pallidum: not only is it non-culturable (for more than a few generations), but the few genomes examined to date show little variation. Hence, successful sequencing of whole genomes offers the potential to identify a larger set of polymorphic sites that will be useful for detailed population genomics analyses.

Research Aims

Currently, we are using next-generation technologies to examine the genetic variation of the bacterial strains responsible for syphilis in Switzerland and other countries. By investigating patterns of diversity and differentiation, and the phylogenetic relationships among strains, we aim to enhance our epidemiological understanding of the re-emergence of syphilis in developed nations.

Specific Goals

  • Develop optimized next-generation methods for the whole genome sequencing of Treponema pallidum pallidum from clinical samples
  • Identify a genome-wide marker set of polymorphic locifor population genomics analyses
  • Examine patterns of genetic diversity and differentiation across and within countries

To achieve our aims, we have established a network of international collaborators working in the medical, clinical, epidemiological and genomic fields.


The project is funded since 2012 by the Forschungskredit (University of Zurich) and the Evolutionary Genetics and Theoretical Biology group (Institue of Evolutionary Biology and Environmental studies).

Dobay A., Gall GEC., Rankin DJ., Bagheri HC. (2013). Renaissance model of an epidemic with quarantine. Journal of Theoretical Biology, 317:348-358. DOI: 10.1016/j.jtbi.2012.10.002.

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