High seroprevalence of human metapneumovirus infection in children in Chongqing, China

Background The human metapneumovirus （hMPV） is a newly discovered respiratory viral pathogen that was first isolated in 2001 in the Netherlands. Its global distribution and long history of infection in humans have been well documented. In this study, we assessed the seropositivity of hMPV IgG antibodies in children in Chongqing, China. Methods The specificity of the enzyme linked immunosorbent assay （ELISA） was first validated by using respiratory syncytial virus （RSV） infected, antigen subtracted reference serum and by performing western blotting using anti-hMPV animal serum. This assay was used to determine the presence of the IgG antibody against hMPV and RSV in 325 serum samples obtained from children aged 0-6 years. Results No crossreaction was detected by ELISA between the antibodies to hMPV and RSV. The seropositivity of the anti-hMPV IgG antibody was 74.5% in children aged 0 to 5 months, 64.0% in 6 to 11 months, 72.7% in 12 to 23 months, 87.1% in 24 to 35 months and 90.3% in 3 to 6 years. Conclusions hMPV is a common and significant respiratory pathogen in Chinese children. Almost all individuals are exposed to hMPV by age 6 years.