1 Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK. a.rambaut@ed.ac.uk.
2 Marie Bashir Institute for Infectious Diseases and Biosecurity, School of Life and Environmental Sciences and School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia. edward.holmes@sydney.edu.au.
3 Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK.
4 Department of Medicine, University of Cambridge, Cambridge, UK.
5 Department of Zoology, University of Oxford, Oxford, UK.
6 Department of Zoology, University of Oxford, Oxford, UK. oliver.pybus@zoo.ox.ac.uk.