1. Centers for Disease Control and Prevention, Atlanta, Georgia, USA; †Secretaria de Salud, Mexico City, Mexico
2. San Diego County Health and Human Services Agency Public Health Laboratory, San Diego, California, USA
3. Instituto de Diagnóstico y Referencias Epidemiológicas, Mexico City, Mexico
4. Universidad Nacional Autonoma de Mexico, Mexico City, Mexico
5. Instituto de Servicios de Salud Publica de Baja California, Mexicali, Baja California, Mexico
6. California Department of Health Services, San Diego, California, USA
7. Secretaria de Salud Publica, Hermosillo, Sonora, Mexico
8. Arizona Department of Health Services, Tucson, Arizona, USA
9. Servicios de Salud de Chihuahua, Chihuahua, Chihuahua, Mexico
10. New Mexico Department of Health, Santa Fe, New Mexico, USA
11. Border Epidemiology Center, Las Cruces, New Mexico, USA
12. Texas Department of Health, Austin, Texas, USA
13. Servicios de Salud de Tamaulipas, Ciudad Victoria, Tamaulipas, Mexico
14. Pan American Health Organization, El Paso, Texas, USA