Clinical characterization of hospitalized children infected with human metapneumovirus and the virus genetic characters

Objective To investigate the clinical manifestation of hMPV in infants and young chil-dren presented with acute respiratory tract infection and to identify the molecular character. Methods Na-sopharyngeal aspirates were taken from 310 hospitalized pediatric patients from February to May in 2006, March to April in 2008, and September 2008 to February 2009, and the N gene fragments of hMPV were de-tected by nested PCR amplification. Phylogenetic analysis of 17 strains hMPV N genes was performed. The clinical materials of patients were collected and analyzed. All hMPV-positive samples were examined by multi-PCR for other respiratory viruses. Results Of 310 pediatric patients, 20 (6.5%) were positive for hMPV. The median age of hMPV infected children was 15.0 months(from 16 days to 9 years old), 90% (18/20)of the cases were under 2 years, and 60% were male. Phylogenetic analysis of 17 N gene fragments showed that 11 hMPV strains were A2b subtype. 20 hMPV-positive children were subjected to pneumonia, accounting for 7.1% (20/282) among all pneumonia subjects in this study. The common clinical manifesta-tions of hMPV infected patients were cough, wheezing, shortness of breath and fever. 35% (7/20) needed intensive care, 15% (3/20) were given oxygen therapy. The median length of hospital stay was (11.9 ±4.8) d. No significant seasonal distribution of hMPV was displayed. Two patients were coinfected with ade-novirus and rhinovirus respectively. Conclusion hMPV was an important respiratory pathogen in young children subjected to pneumonia in Tianjin. Three subtypes(A2a/A2b, B1, B2) were prevalent in Tianjin, and A2b was the predominant subtype. No significant difference of clinical characters was observed between A and B type hMPV infected patients. Key words: Respiratory infection;  Human metapneumovirus;  Phylogenetic analysis;  Child