1 Alpert Medical School of Brown University, Providence, Rhode Island, USA.
2 Center for Public Health Research, Kenya Medical Research Institute, Nairobi, Kenya.
3 Department of Global Health.
4 Department of Epidemiology.
5 Medicine, University of Washington, Seattle, Washington, USA.
6 University of Nairobi College of Health Sciences, Institute of Tropical and Infectious Diseases, Partners for Health and Development in Africa, Nairobi, Kenya.
7 Department of Emergency Medicine, Alpert Medical School of Brown University, Providence, Rhode Island, USA.