1. Department of Medical Education, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán , Mexico City , Mexico
2. Division of Postgraduate Studies, Faculty of Medicine, Universidad Nacional Autónoma de México , Mexico City , Mexico
3. Unit of Epidemiology, Institute of Environmental Medicine, Karolinska Institutet , Stockholm , Sweden
4. Department of Infectious Diseases, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán , Mexico City , Mexico
5. High Specialty Regional Hospital Bajio, Health Secretariat , León , Mexico
6. Consorcio de Investigación en Salud , Cuernavaca , Mexico