Human metapneumovirus infections in hospitalised infants in Spain

Background: Human metapneumovirus (hMPV) causes lower respiratory tract infections, particularly in young children and the elderly. Methods: A prospective study was conducted on the clinical characteristics of infants, 2 years of age admitted to hospital for respiratory infection and the characteristics of hMPV infections were compared with those of infections caused by respiratory syncytial virus (RSV). Influenza A, B and C viruses, RSV, parainfluenza viruses, and adenoviruses were simultaneously detected in clinical samples by multiple reverse transcription nested-PCR assay. The presence of hMPV was tested in all samples using two separate RT-PCR tests. Results: A respiratory virus was detected in 65.9% of the 749 children included in the study. hMPV, found in 69 of the positive nasopharyngeal aspirates (14%), was the most common virus after RSV. Peak incidence was in March and over 80% of children were,12 months of age. The most common diagnoses were recurrent wheezing (49.3%) and bronchiolitis (46.4%). Oxygen therapy was required by 58% of patients, and assisted ventilation by one. Clinical characteristics in the 18 co-infections were indistinguishable from those of single infections. Fifty one hMPV single infections were compared with 88 hRSV single infections. Recurrent wheezing was diagnosed more frequently in hMPV patients. All other variables tested were similar in both groups. Conclusions: hMPV was the second most frequent virus after RSV in infants,2 years of age hospitalised for respiratory infection and was associated with lower respiratory tract infections. hMPV occurred predominantly in springtime. Co-infections were frequent and clinically similar to single infections and RSV infections.