Dating the emergence of human pathogens

Understanding the emergence and evolution of human pathogens plays a pivotal role in epidemiology and in predicting the trajectories of outbreaks. The application of phylogenetic methods to pathogen genomes has provided a range of insights into their evolutionary dynamics (1). In many cases, phylogenetic methods can use the sampling dates of the genomes to reconstruct the evolutionary time scales of viruses, bacteria, and other pathogens. Ancient genomes can increase the power of these approaches by narrowing the estimated time window of pathogen emergence and by augmenting the evolutionary temporal signal in the genetic data. On page 1367 of this issue, Düx et al. (2) show how a century-old genome of Measles morbillivirus, extracted from human lung tissue, can help efforts to pinpoint the time of emergence of measles