Epidemiological and genetic characteristics of human metapneumovirus in pediatric patients across six consecutive seasons in Beijing, China.

• There was a higher incidence of human metapneumovirus (hMPV) infection in inpatients than outpatients. • A biennial alternating pattern of hMPV infection, fluctuating with hMPV activity, was observed. • There was a clear-cut demarcation between the end of one season and the start of the next. • hMPV activity increased with the apparent decline in influenza activity. To investigate the genetic characteristics of human metapneumovirus (hMPV) circulating among children with acute respiratory tract infections (ARTIs) in Beijing, China. Clinical samples were obtained from outpatients and hospitalized children with ARTIs between August 2010 and July 2016. Reverse transcription polymerase chain reaction assays were used to screen and identify hMPV, while partial glycoprotein gene sequences were used for phylogenetic analysis. Among the 10 918 samples, 292 (2.7%) were positive for hMPV. Overall, the virus was more prevalent among inpatients (4.3%) than outpatients (1.2%). A biennial alternating pattern of hMPV infection was observed, with infection rates fluctuating between 1.6% and 4.0%. Most cases were detected between December and April, showing clear-cut seasonality. Sub-genotypes A2b, B1, and B2 co-circulated in winter and spring in an alternating pattern, while only one A1-positive case was observed in 2012. The seasonal peak of hMPV was slightly delayed or overlapped with that of respiratory syncytial virus and influenza virus. hMPV activity increased in the 2010–2011 and 2014–2015 seasons, when influenza activity was apparently decreased compared with other epidemic seasons. This study provides information on the epidemiological and genetic characteristics of hMPV in children in Beijing, and reinforces the significance of hMPV in children with ARTIs, especially lower respiratory tract infections. [ABSTRACT FROM AUTHOR]