1. Centro de Estudios en Salud, Universidad del Valle de Guatemala , Guatemala City , Guatemala
2. Centre for Research in Infectious Diseases, National Institute of Respiratory Diseases , Mexico City , Mexico
3. Ministerio de Salud de El Salvador , San Salvador , El Salvador
4. Centro de Estudios en Salud, Universidad del Valle de Guatemala , San Salvador , El Salvador
5. US Centers for Disease Control and Prevention, Central American Region , Guatemala City , Guatemala
6. Pan-American Health Organization , Washington, District of Columbia , USA
7. Coordinating Commission of the Mexican National Institutes of Health , Mexico City , Mexico