Genomic data has become an increasingly widely used source of information in the fight against infectious disease outbreaks. Often called "genomic epidemiology", the mutations observable in a pathogen's genome allow us to reconstruct its distribution, spread and evolution over time. Nowhere has this been more clearly demonstrated than during the COVID-19 pandemic. Since early 2020, the global scientific community has come together to generate over 15 million SARS-CoV-2 genome sequences, data which has been critical for identifying the emergence of variants of concern, spillover to non-human reservoirs, reconstructing transmission networks and much more. Advances in analysis, improved study designs and greater integration with epidemiological and clinical data present exciting opportunities to further extend the insights provided by pathogen genomic data. In this talk, I will present applications of genomic epidemiology at diverse scales from recent research, using the example of SARS-CoV-2, and consider lessons, opportunities and challenges for the future of genomic surveillance