1. ICPSR, University of Michigan , Ann Arbor, Michigan , USA
2. School of Public Health, University of Michigan , Ann Arbor, Michigan , USA
3. Centro Nacional de Diagnóstico y Referencia, Ministry of Health , Managua , Nicaragua
4. Sustainable Sciences Institute , Managua , Nicaragua
5. Centro de Salud Sócrates Flores Vivas, Ministry of Health , Managua , Nicaragua