Over the last few decades, an age-old infectious disease has been re-emerging globally: syphilis. Using techniques to analyze low levels of DNA, an international research team has now shown that all syphilis strains from modern patient samples share a common ancestor from the 1700s. Furthermore, their research demonstrates that strains dominating infections today originate from a pandemic cluster that emerged after 1950, and these strains share a worrying trait: resistance to the second-line antibiotic azithromycin.