1. Department of Health Behavior and Health Education, School of Public Health, University of Michigan, Ann Arbor, Michigan.
2. School of Public Health and Institute for Behavioral and Community Health, San Diego State University, San Diego, California.
3. Division of Infectious Disease and Global Public Health, University of California San Diego, La Jolla, California.
4. School of Medicine, Universidad Xochicalco, Tijiuana, Mexico.