Prevalence and clinical and molecular characterization of human metapneumovirus in children with acute respiratory infection in China.

Background: Human metapneumovirus (HMPV), a newly discovered paramyxovirus, has been associated with acute respiratory tract infections (ARTIs). However, the prevalence and molecular characteristics of HMPV in China are still unclear. Methods: A total of 661 nasopharyngeal aspirates (NPA) specimens were collected from 661 children with ARTIs between December 2006 and November 2008. Specimens were screened for HMPV by reverse transcription-polymerase reaction. All positive amplification products were confirmed by sequencing. Results: HMPV was detected in 45 patients (6.80%) of the 661 children. The HMPV-infected patients were from 29 days to 9 years of age. A high incidence of HMPV infection (84.4%) was observed during the winter-spring season. Of the 45 HMPV-positive patients, 25 (55.6%) were co-infected with other respiratory viruses, and respiratory syncytial virus (RSV) was the most common additional respiratory virus. The most common clinical diagnosis was bronchopneumonia (57.8%) and cough (88.9%) was the most common clinical symptom. Phylogenetic analysis of the F gene revealed that 80% of the HMPV detected were A2, 2.2% were A1, and 17.8% were B1. Statistical analyses showed that sex, ages, seasons, and severity of the disease did not correlate with HMPV genotype (P = 0.986, 0.347, 0.660, 0.252), but viral coinfection with HMPV increased hospitalization rates (P = 0.005). Conclusions: HMPV was frequently detected in the pediatric patients with ARTI in China. RSV was the most common coinfection virus and coinfection increased hospitalization rates. All HMPV subgroups except B2 cocirculated and there was no association found between HMPV genotypes and severity of disease.