Frequency of respiratory viruses in infants with severe respiratory infection admitted to neonatal intensive care unit, Milan (Italy), 2015 and 2016

BACKGROUND-AIM Severe acute respiratory infections (SARI) are a leading cause of hospitalization and death in children. We report the frequencies of respiratory viruses molecularly detected in samples collected from infants with SARI admitted to the neonatal intensive care unit (NICU) of a University and research hospital in Milan (Italy) in 2015 and 2016. METHODS 217 respiratory specimens collected from as many children aged less than 1 year (median age: 1.1 months; IQR: 2.1 months) who required NICU admission due to SARI were analysed. After nucleic acid extraction (EZ1®DSP Kit, Qiagen), samples were tested by a multiplex real-time PCR (Anyplex™ II, RV16-Detection, Seegene) to detect: Adenovirus (AdV), Bocavirus (BoV), Coronavirus (CoV), Parainfluenza virus (PIV), Metapneumovirus (MPV), Enterovirus (EV), Respiratory syncytial virus (RSV), Rhinovirus (RV), and Influenza virus (IV). RESULTS 40.6% (88/217) of samples were positive for at least one of the studied viruses; more than one virus was detected in 9.1% (8/88) of these positive-specimens. A viral infection was recognized in 48.5% (48/99) of neonates (infants <1 month of age). RV, RSV and PIV were the 3 main contributors, detected in 88.6% (78/88) of positive-samples (48.9%, 28.4% and 11.4%, respectively). 17% (15/88) of positive-samples tested positive for EV, BoV or CoV (5.7% each). AdV, MPV and IV were identified in less than 6% of positive-samples (2.3%, 2.3% and 1.1%, respectively). About half (41/77; 53.2%) of positive-samples was recorded from December to March, when 31.7% (13/41) of RV and 41.5% (17/41) of RSV infections occurred. All EVs were detected in the last 10 days of May 2015. CONCLUSIONS In our SARI series, at least one virus was identified in 40% of cases and nearly half occurred in neonates. The main contributor was RV, followed by RSV and PIV. In this study, the other viruses were low-frequency identified. Respiratory viruses were detected throughout the year, though more than half were recognized during winter months. Routine molecular diagnosis of respiratory viruses in infants with SARI requiring NICU should be strongly encouraged to quickly identify the involved pathogens, to assess their spread and recognise outbreaks and to drive treatment, thus avoiding the useless administration of antibiotics in such young patients.