Population-based incidence of human metapneumovirus infection among hospitalized children

Abstract

Background: Human metapneumovirus (HMPV) is a leading cause of acute respiratory illness (ARI) in children. Population-based incidence rates and comprehensive clinical characterizations of disease have not been established.

Methods: We conducted population-based prospective surveillance for 2 years in 2 US counties of HMPV infection among children <5 years old who were hospitalized with ARI or fever. Nasal and throat specimens obtained with swabs were tested for HMPV by real-time reverse-transcription polymerase chain reaction and genotyped.

Results: Forty-two (3.8%) of 1104 children tested positive for HMPV. The overall annual rate of HMPV-associated hospitalizations per 1000 children <5 years old was 1.2 (95% confidence interval [CI], 0.9-1.6). This rate was highest among infants 0-5 months old (4.9 per 1000 [95% CI, 2.9-7.2]), followed by children 6-11 months old (2.9 per 1000 [95% CI, 1.4-4.7]). The annual rate of hospitalization for HMPV infection was less than that for respiratory syncytial virus infection but similar to that for influenza and parainfluenza virus 3 infection in all age groups. The mean age of children hospitalized with HMPV infection was 6 months. Bronchiolitis, pneumonia, and asthma were the most common diagnoses among children with HMPV infection. All 4 HMPV subgroups were detected during both years at both sites. HPMV infection was most prominent from March through May.

Conclusion: HMPV was detected in 3.8% of children hospitalized with ARI or fever, with a population incidence similar to that of influenza virus and parainfluenza virus 3.

Table 1.

Characteristics of Hospitalized Children with Human Metapneumovirus (HMPV) Infection Compared with Those of Other Study Children

Table 2.

Incidence of Hospitalization Attributable to Infection with Human Metapneumovirus (HMPV) and Other Common Respiratory Viruses among Children <5 Years Old

Figure 1.

Number of specimens submitted and number of specimens that tested positive for human metapneumovirus (HMPV), by month. Data are combined from 2 years.

Table 3.

Clinical Features of Human Metapneumovirus-Positive and Human Metapneumovirus-Negative Hospitalized Children

Figure 2.

Subgroups of the isolates of human metapneumovirus (HMPV) detected during study period.

Figure 3.

Phylogenetic tree depicting the relationships among human metapneumovirus (HMPV) F sequences (A) and G sequences (B) identified in this study. Phylogeny was inferred using the neighbor-joining method with 500 bootstrap replicates, as described in Methods. Branches reproduced in <50% of the bootstrap replicates are collapsed. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test is shown next to the branches. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. Diamonds , prototypical GenBank strains. The scale bar indicates nucleotide substitutions per site. Sequences identified in this study have been submitted to GenBank.