Clinical and epidemiologic characteristics of viral infections in a neonatal intensive care unit during a 12-year period

Background: The incidence of viral infections in patients treated in the neonatal intensive care unit (NICU) is not well-known. We summarized the data of all patients with laboratory-confirmed viral infections admitted at the NICU of our hospital during the period of 1992-2003. Objectives: To determine the incidence of viral infections among infants hospitalized in a NICU, the associated clinical manifestations and their outcome. Methods: Retrospective analysis of epidemiologic, virologic and clinical data from infants with proven viral infection. The diagnosis viral infection was confirmed by positive viral culture and/or polymerase chain reaction from clinical samples. Results: Viral infection was confirmed in 51 of 5396 infants (1%) admitted to the NICU; 20 (39%) had an enterovirus and parechovirus (EV/PEV) infection, 15 (29%) a respiratory syncytial virus (RSV) infection, 5 (10%) a rotavirus infection, 3 (6%) a cytomegalovirus (CMV) infection, 2 (4%) an adenovirus infection, 2 (4%) a parainfluenza virus infection, 2 (4%) a herpes simplex virus infection, 1 (2%) a rhinovirus infection and 1 (2%) a rubella virus infection. Three of the infants presented at birth with symptomatic rubella virus, CMV or herpes simplex virus infection. RSV infection developed mostly in hospitalized infants (60%), and 93% of infections occurred during the winter (November-March). The clinical presentations of EV/PEV disease were sepsis-like illness, prolonged seizures in term infants and gastrointestinal disease in preterm infants. RSV, parainfluenza virus, rhinovirus and CMV caused respiratory disease, predominantly in preterm infants. Gastrointestinal disease was seen only in preterm infants with adenovirus, rotavirus or EV/PEV infection. Mortality and serious sequelae were high in patients infected with EV/PEV (10 and 15%, respectively). Conclusions: The incidence of viral infection in the NICU was 1%. Enteroviral infections were the most frequently diagnosed infections, occurred often in term infants born at home and presented with sepsis-like illness or seizures. Preterm infants hospitalized from birth mainly developed gastrointestinal disease caused by rotavirus and adenovirus infection or respiratory disease caused by RSV, parainfluenza and CMV infection. Enteroviruses were responsible for the highest mortality and development of serious sequelae.