Prevalence and characteristics of human metapneumovirus infection among hospitalized children at high risk for severe lower respiratory tract infection

Background: Human metapneumovirus (HMPV) is a significant cause of respiratory tract infections. Little is known about HMPV in children who are at high risk for lower respiratory tract infection (LRTI). Methods: To determine the prevalence of HMPV in high-risk children and to identify HMPV risk factors, children ≤24 months with prematurity, chronic lung disease, and/or congenital cardiac disease who were hospitalized with LRTI were prospectively enrolled. Nasopharyngeal aspirates were tested for HMPV, respiratory syncytial virus (RSV), influenza A and B, and parainfluenza types 1-3. Demographics, medical history, and outcomes for those with HMPV and RSV were compared. A multivariate analysis was performed to determine HMPV risk factors. Results: Over 4 years, 1126 eligible children were enrolled. Pathogens were identified in 61% of subjects. HMPV was identified in 9.0%, second to RSV (45%). Coinfection with HMPV and RSV occurred in <1% of subjects. Subjects infected with HMPV were older (8.2 vs 4.0 months, P < .001), were born more prematurely (27 vs 33 weeks, P < .001), and more commonly had chronic lung disease (59.3% vs 21.8%, P < .001) compared with subjects infected with RSV. In a multivariate analysis that compared children infected with HMPV to all others, increasing age and household exposure to children ages 6-12 were associated with an increased risk, whereas birth at older gestational age and exposure to children age >12 were associated with a decreased risk. Conclusions: HMPV was detected in 9% of high-risk children who were hospitalized with lower respiratory tract disease, representing the second most common virus in this population. Compared with all other subjects (including RSV-infected), subjects infected with HMPV were older but were born more prematurely.