This work was supported by the United States Agency for International Development (USAID) Emerging Pandemic Threats PREDICT project [Cooperative Agreement No. AID-OAA-A-14-00102] and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health [Award No. R01AI110964]. The contents are the responsibility of the authors and do not necessarily reflect the views of USAID, the United States Government or the National Institutes of Health.