Respiratory viral infections are not uncommon in neonatal intensive care units

Abstract

Full-term and preterm infants admitted to neonatal intensive care units (NICUs) face a high risk of infections, due to the immaturity of their innate and adoptive immune systems, inadequate protection through maternal immunity and the need for repeated invasive procedures (1). In recent years, our knowledge of viral infections in neonates has increased, due to multiplex polymerase chain reaction (PCR)-based techniques. It is now possible to screen for as many as 17 viruses from a single mucus sample (2). However, the role of viral respiratory tract infections in the symptoms of infants admitted to NICUs at birth is still poorly understood. In a recent review, 32 respiratory viral outbreaks in NICUs were reported (3). These were caused by several different respiratory viruses, including respiratory syncytial virus (RSV) (89 patients in 11 outbreaks), enteroviruses (101 patients in 10 outbreaks) and adenovirus (79 patients in six outbreaks). In addition, outbreaks of coronavirus, rhinovirus, influenza A virus and parainfluenza virus infections have been reported (4–7). An epidemic may result in the temporary closure of a NICU. Recently, a NICU was closed for 28 days after adenovirus type 19 caused an outbreak of keratoconjunctivitis, which affected 12 NICU infants, two NICU staff members, two relatives of patients and two members of the ophthalmologic team (8). We report on an observational study on the use of a multiplex PCR in a NICU in Finland. The study was carried out at Turku University Hospital, the only tertiary level NICU in south-west Finland, which serves a population of about 750 000. An average of 600–700 infants are admitted to the NICU annually, resulting in approximately 6000 patient care days per year. About one-third of the infants are preterm, and 50–85 very low birth weight infants are treated annually. Two to four patients are treated in one room. Parents are encouraged to stay with their infant and provided with unlimited access. Visitors with respiratory tract infection symptoms are not allowed into the NICU, and siblings under school age cannot visit if there is an RSV outbreak in the community. Otherwise, healthy siblings are allowed access. During the study period from 1 January 2009 to 30 June 2011, 1589 infants were admitted to the unit and 76 (5%) were evaluated for respiratory viruses. A nasopharyngeal aspirate was taken from infants if they presented with symptoms of respiratory infection, such as rhinorrhea, sneezing, increased bronchial secretions, episodes of bradycardia and/or desaturations, or if they had been exposed to someone with a respiratory infection. We collected and analysed 139 samples from 76 infants for this study. Nasopharyngeal aspirates were collected in sterile tubes and analysed on the same or following day. Nucleic acids were extracted from the aspirates using Nuclisense easyMag extractor (Biomerieux, Boxtel, the Netherlands). Respiratory virus genomes were detected using Seeplex RV12 multiplex PCR assay for adenovirus, influenza A and B viruses, parainfluenza types 1–3 viruses, RSVa, RSVb, rhinovirus, human metapneumovirus, and coronaviruses 229E/NL63 and OC43/HKU1 (Seegene, Seoul, Korea). In addition, specimens were tested in a real-time PCR assay for enteroviruses, rhinovirus and RSV (9). During the two-and-a-half-year study period, no outbreaks of viral respiratory tract infection occurred in the NICU. Of the 139 samples taken from 76 infants, 28 samples (20%) from 15 infants (20%) were positive for one or more viruses. Six babies were positive for rhinovirus, five for parainfluenza type 3 virus, one for parainfluenza type 2