1. Department of Epidemiology, Municipal Centre of Hygiene, Epidemiology and Microbiology, Calle 8 No. 406 Esquina a 19, Vedado, 10400 La Habana, Cuba
2. Department of Gastro-enterology, Nutrition and Parasitology, Academic Paediatric Hospital “Pedro Borrás”, Calle F No. 616 Esquina 27, Vedado, 10400 La Habana, Cuba
3. Department of Child Health, National Institute of Hygiene, Epidemiology and Microbiology, Calle Infanta No. 1158 Esquina a Llinas, Cerro, 10300 La Habana, Cuba
4. Department of Child Health, Faculty of Medicine “Comandante Manuel Fajardo”, Calle D esquina a Zapata, Vedado, 10400 La Habana, Cuba
5. Gastro-intestinal unit, Department of Paediatrics, Academic Paediatric Hospital “Centro Habana”, Benjumeda y Morales, Cerro, 10600 La Habana, Cuba
6. Department of Infectious diseases, Institute of Infectious Diseases “Emilio Ribas”, Rua Zacarias de Gois, 966/41 São Paulo, SP, Brazil