Proportions of tested serum samples with different titers of anti-hMPV and anti-hRSV antibodies within different age groups. Cumulative percentages of anti-hMPV and anti-hRSV antibodies detected in samples from each age group. The percentage of samples with corresponding titers of anti-hMPV and anti-hRSV IgG antibodies are indicated by different colors defined in the figure key. Titers are expressed as the reciprocal of the fold dilution. A total of 160 human serum samples that were seropositive for hMPV or hRSV were randomly selected for ELISA using hMPV N protein or hRSV N protein as the antigen. M, hMPV; R, hRSV.