1. Center for Human Development, Fundación para la Salud Integral de los Guatemaltecos, Retalhuleu 11010, Guatemala
2. Center for Global Health, Colorado School of Public Health, Aurora, CO 80045, USA
3. Department of Epidemiology, Colorado School of Public Health, Aurora, CO 80045, USA
4. Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY 11032, USA
5. Centers for Disease Control and Prevention (CDC), Atlanta, GA 30333, USA
6. Centro de Estudios en Salud, Universidad del Valle de Guatemala, Guatemala City 01015, Guatemala
7. Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, USA