Epidemiological analysis and clinical study of pediatric human metapneumovirus detected in patients with acute respiratory infection]

We detected and isolated human metapneumovirus (HMPV) and isolated another respiratory virus in pharyngeal swab specimens from 502 pediatric patients with acute respiratory infection, seen at 3 Kyoto City sentinel hospitals from January to December 2011. Our prospective study detected 43 positive HMPV cases (8.6%). Phylogenetic analysis showed that subgroup A2 was most common, followed by B1 and B2, and that A1 was not detected. HMPV was detected mostly in specimens from patients less than 3 years old, and positive HMPV was identified most in spring, peaking in March. Our clinical study showed that positive HMPV patients had fever above 38 degrees (86%) and cough (65%). Among the 30 whose chest radiography was examined, radiological findings were recognized in 18 cases. We found inflammatory infiltrative shadows around the bronchus and peribronchus near the hilum of the lung. Lobar pneumonia and diffuse infiltrative shadows coinciding with peripheral alveolar involvement were not recognized. No difference affecting illness severity was seen among subgroups, viral isolation results, or mixed coxsackie virus or influenza virus infection. In hospitalization, mean disease lasted significantly longer in those with lower respiratory tract symptoms at first'examination than in those without such symptoms. We detected HMPV RNA in pharyngeal swabs and stool specimens from patients admitted to the hospital for rhabdomyolysis.