Comparison of Clinical Characteristics of Human Metapneumovirus and Respiratory Syncytial Virus Infections in Hospitalized Young Children.

Human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) are the leading causes of acute respiratory tract infection in children, and clinical manifestations of these virus infections are considered similar. To investigate the differences in clinical characteristics between HMPV and RSV infections in young children, we prospectively enrolled children ＜ 3 years old who required hospitalization with acute respiratory tract infection due to HMPV or RSV at 10 hospitals in Japan. We enrolled 48 children with HMPV infection and 141 with RSV infection. Patients with HMPV infection were older than those with RSV infection. High-grade fever was more frequently observed in patients with HMPV infection, whereas no significant differences in respiratory symptoms were apparent. Abnormal serum lactate dehydrogenase values and consolidation shadows on chest X-ray were more frequently observed in patients with HMPV infection. During hospitalization, nasal mucus suction was more frequently required in patients with RSV infection. On the other hand, β2-adrenergic agonists, corticosteroids, and leukotriene receptor antagonists were more frequently used in patients with HMPV infection. These findings suggest that HMPV and RSV infections show similar respiratory symptoms, but HMPV infection is more likely to lead to the development of pneumonia, at least among hospitalized young children.