- Objectives To determine the involvement of human metapneumovirus (HMPV) in childhood community-acquired alveolar pneumonia (CAAP) and compare the demographic, clinical, and laboratory features of HMPV-associated CAAP and CAAP associated with other respiratory viruses. Study design Nasopharyngeal wash specimens obtained prospectively over a 4-year period from children age < 5 years evaluated in the emergency department with radiologically diagnosed CAAP and from healthy controls were tested for HMPV by reverse-transcriptase polymerase chain reaction and for respiratory syncytial virus (RSV), adenovirus, influenza and parainfluenza viruses by direct immunofluorescence and culture. Results HMPV was detected in 108 of 1296 patients (8.3%) versus RSV in 23.1%, adenovirus in 3.4%, influenza A virus in 2.9%, and parainfluenza viruse in 2.9%. During the period of peak activity (November to May), HMPV was detected in 95 of 1017 patients (9.3%) and in 3 of 136 controls (2.2%) (P = .005). The patients with HMPV were older than those with RSV (P < .001) with a more common history of acute otitis media requiring tympanocentesis (P = .032), wheezing (P = .001) and gastrointestinal symptoms (P < .001) and a lower hospitalization rate (P = .005). Conclusions The high detection rate suggests an important role for HMPV in childhood CAAP. Our findings identify demographic and clinical features of HMPV-positive CAAP and its age-related impact on hospital admissions.