It's been ten years since scientists sequenced the Treponema pallidum bacterium, which causes syphilis. However, while at the time hailed as a milestone that would conquer the disease, having sequence information hasn't stopped the spread of syphilis. Scientific American interviews the CDC epidemiologist Hillard Weinstock on why he sees syphilis rates climbing since 2000 -- "We need to remember that in historical context, the number of syphilis cases we see today is relatively low," he says -- and how different epidemiological and social factors come into play.