Population-Based Incidence of Human Metapneumovirus in Hospitalized Children

Williams, John V.; Edwards, Kathryn M.; Weinberg, Geoffrey A.; Griffin, Marie R.; Hall, Caroline B.; Zhu, Yuwei; Szilagyi, Peter G.; Wang, Chiaoyin K.; Yang, Chin-Fen; Silva, David; Ye, Dan; Spaete, Richard R.; Crowe, James E.

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 HMPV in two U.S. counties among children <5 years hospitalized with ARI or fever for two years. Nasal/throat swabs were tested for HMPV by real-time RT-PCR and genotyped. RESULTS: Forty-two of 1104 (3.8%) children tested positive for HMPV. The overall annual rate of HMPV-associated hospitalizations per 1000 children <5 years was 1.2 (95%CI 0.9–1.6). This rate was highest in infants 0–5 months (4.9/1000 [95%CI 2.9–7.2]), followed by children 6–11 months (2.9/1000 [95%CI 1.4–4.7]). The annual rate of HMPV-associated hospitalizations was less than respiratory syncytial virus, but similar to influenza and parainfluenzavirus (PIV) 3 in all age groups. The mean age of children hospitalized with HMPV was 6 months. Bronchiolitis, pneumonia and asthma were the most common diagnoses in children with HMPV. All four HMPV subgroups were detected during both years at both sites. HPMV was most prominent from March through May. CONCLUSIONS: HMPV was detected in 3.8% of children hospitalized with ARI or fever, with a population incidence similar to that of influenza and PIV3.