Seroprevalence of IgG antibodies against hMPV and hRSV. A total of 1,156 serum specimens were tested. Anti-hMPV and anti-hRSV IgG antibodies were detected using the N-ELISA method (see Methods) at a dilution of 1:200. All serum samples were grouped based on age, as indicated at the bottom of each panel. The percentage of positive samples in each group is listed above each data point.