1. Division of Infectious Diseases and Immunology, Department of Medicine, Chan Medical School, University of Massachusetts, Worcester, MA 01605, USA
2. Center for Global Health Research, Kenya Medical Research Institute, Kisumu 40100, Kenya
3. Department of Pathology and Laboratory Medicine, Warren Alpert Medical School, Brown University, Providence, RI 02903, USA
4. Division of Infectious Diseases, Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
5. Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA
6. Viral Immunobiology, Institute of Experimental Immunology, University of Zurich, CH-8057 Zurich, Switzerland