1. Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, California.
2. Division of Veterinary Public Health, School of Veterinary Medicine, Institute for Risk Assessment Sciences, University of Utrecht, Utrecht, the Netherlands.
3. Unidad de Investigación Médica en Inmunología, Hospital de Pediatría, Centro Médico Nacional Siglo XXI, IMSS, Mexico City, Mexico.
4. Instituto de Diagnóstico y Referencia Epidemiológicos, Mexico City, Mexico.