ESPGHAN and NASPGHAN agree on the same definition that can be summarised as follows: Acute gastroenteritis (AGE) is a common occurrence in infancy caused by viral or bacterial infections (e.g. Rotavirus, Norovirus, Campylobacter or Salmonella). AGE generally manifests itself as a decrease in stool consistency (loose or liquid) and/or in an increase of evacuation frequency (typically three or more times in 24 hours). It may or may not be accompanied by vomiting or fever. Because of the decrease in stool consistency acute gastroenteritis is related to acute diarrhoea (Guarino et al., 2018, Guarino et al., 2014).