Of 258 wheezing children, 111 (43%) had serologic evidence of past infection; 48 (19%) of acute primary HBoV infection (Table 1; Figure 2 ). Of the latter group, 32 had detectable IgM with either IgG conversion (27/48) or a diagnostic increase (5/48); a total of 15 had IgM with no IgG (5/48) or with a constant IgG (10/48) absorbance value. A girl 1 year of age showed seroconversion in a convalescent-phase serum sample weakly positive for IgG but she had no IgM in either sample (Table 1 ). All other children who showed seroconversion or an increase in IgG were IgM positive. Incidence rates of serologically verified, acute, primary HBoV infection among wheezing children varied with age, with a peak of 28% in children 1-<2 years of age (Table 2) . Prevalence of HBoV immunity increased with age, reaching 100% at 7 years of age (Table 2 ). This study included 27 (10%) of 258 children <6 months of age (median 4.8 months, mean 4.7 months). Eight (30%) of 27 children were IgG positive; IgG in 7 of these children was presumably of maternal origin. One infant (3.7%), a 3.6-month-old boy, had a serologically verified acute HBoV infection. (10) was not included in this comparison because of depletion of the convalescent-phase serum sample before the PCR (NPA and acute-phase serum samples were PCR negative; both serum samples were IgG positive and IgM negative, indicating immunity). Comparison of qPCR and EIA results for 258 children is shown in Table 1 . Among 49 children who showed viremia, 45 (92%) had a serodiagnosis of HBoV infection: i.e., had IgM or an increase in IgG. Of the remaining 4 viremic children, 1 was seropositive and 3 were seronegative; 2 of the seronegative children showed viremia in a second sample, possibly indicating a very acute infection (their NPA samples at the time of admission had been PCR negative). Among 209 nonviremic children, 206 (99%) showed nondiagnostic serologic results (Table 1) . Only 3 (1.4%) of 209 children had a serodiagnosis: the 1-year-old girl with an apparent false seroconversion described above and 2 children with PCR-positive NPAs and a positive result for IgM but a constant IgG level, which suggests a subacute infection.