When an infectious disease outbreak occurs, public health officials attempt to identify where it started and how it spread so that they can initiate appropriate control and prevention strategies. Using a combination of field epidemiology (interviewing cases and controls) and molecular epidemiology (genotyping of bacterial or viral pathogens), they attempt to establish links between cases and develop a putative reconstruction of the outbreak. Unfortunately, the low resolution of molecular epidemiology techniques currently available to most reference microbiology laboratories cannot provide detailed information on the underlying transmission dynamics within an outbreak. However, next-generation sequencing offers exciting new possibilities for tracking disease outbreaks with high resolution. Over the course of an outbreak, a small amount of genetic variation accrues in a pathogen's genome as a result of mutations. By tracking the presence or absence of these mutations in all pathogen genomes from a given outbreak, it is possible to identify where particular variants arose and trace person-to-person transmission events. This webinar will provide an introduction to this emerging field of genomic epidemiology, highlighting the application of this approach to reconstruct outbreaks of tuberculosis in British Columbia, Canada.