Institute for Emerging Infections, Department of Zoology, University of Oxford, The Peter Medawar Building for Pathogen Research, South Parks Road, Oxford, United Kingdom.|Division of Infectious Diseases, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America.|Institute for Emerging Infections, Department of Zoology, University of Oxford, The Peter Medawar Building for Pathogen Research, South Parks Road, Oxford, United Kingdom.