1 Medical Research Council Centre for Global Infectious Disease Analysis, Jameel Institute for Disease and Emergency Analytics, Imperial College London, London SW7 2BU, UK.
2 Department of Zoology, University of Oxford, Oxford, UK.
3 Medical Research Council Centre for Global Infectious Disease Analysis, Jameel Institute for Disease and Emergency Analytics, Imperial College London, London SW7 2BU, UK; Department of Statistics, University of Oxford, Oxford, UK.
4 Department of Mathematics, Imperial College London, London SW7 2BU, UK.
5 Medical Research Council Centre for Global Infectious Disease Analysis, Jameel Institute for Disease and Emergency Analytics, Imperial College London, London SW7 2BU, UK. Electronic address: s.bhatt@imperial.ac.uk.