Nosocomial infections are the most important cause of morbidity and mortality among neonates and mostly in infants admitted to neonatal intensive care units (NICU). The total number of neonates who develop nosocomial infections per admission varies from 6.2 to 30%. The role of nosocomial virus infections is generally neglected in the actual epidemiologic scenario mostly due to the lack of data in the medical literature. Based on a worldwide database of health care-associated outbreaks (http://www.outbreak-database.com) we performed an analysis of the incidence, type of pathogens and clinical features of neonatal viral outbreaks especially those reported in NICUs. We also describe, as an example of emerging virus in NICU, a Norovirus outbreak along with clinical presentation that varies from mild to moderate clinical symptoms like vomiting, gastric remainder, diarrhoea, abdominal distension or severe presentation like necrotizing enterocolitis. and measures implemented for terminating the outbreak. In conclusion, our study analyses the viral origins of nosocomial infections in NICU and underline that the role of viral agents in neonatal nosocomial infections needs to be further investigated even in diseases traditionally considered of bacterial origin like necrotizing enterocolitis.