Salivirus (family Picornaviridae) may be associated with acute gastroenteritis in humans, but there have been no reports of salivirus outbreaks. Salivirus A1 infection with faecal virus concentrations of 2.1-2.6 × 10(9)/g were identified retrospectively in newborn babies, between the ages of 1.5 and 5 days, with apparent clinical symptoms of diarrhea (100 %), fever (40 %), vomiting (40 %), and loss of appetite (40 %) in a neonatal hospital unit in Hungary in July 2013. The complete genome sequence of the salivirus (including the 5'-terminal end) was determined. Salivirus mono-infection may be associated with gastroenteritis in babies who are a few days old. Salivirus testing should be done in public health laboratories in gastroenteritis outbreaks with unknown etiology.