1. Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA 94720-3370, USA.
2. Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA.
3. Infectious Diseases and Immunity Graduate Group, School of Public Health, University of California, Berkeley, Berkeley, CA 94720-3370, USA.
4. Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
5. Division of Genetics, Brigham and Women’s Hospital, Howard Hughes Medical Institute, Department of Genetics, and Program in Virology, Harvard Medical School, Boston, MA 02115, USA.
6. Center for Communicable Disease Dynamics, Department of Epidemiology, and Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115, USA.