Genomic epizootiology of a Brucella abortus outbreak in Northern Ireland (1997–2012)

•We genome sequenced isolates from a recrudescent outbreak of Brucella abortus.•Two major pathogen lineages present. One was linked to a prior epidemic.•Genetic diversity was low, with little spatio temporal signal observed.•Previous VNTR method had suggested more genetic sub-structure than was present.•WGS data has limited use for epizoology of low diversity, recrudescent infections.