The causes of acute lower respiratory tract infection (ALRTI) are mostly attributable to viral infection, including respiratory syncytial virus (RSV), parainfluenza virus (PIV), influenza virus A/ B (IFV A/ B), or adenovirus (ADV). Several Korean studies reported human metapneumovirus (hMPV) as a common pathogen of ALRTI. However, studies on seasonal distribution and clinical differences relative to other viruses are insufficient, prompting us to perform this study.

From November 2006 to October 2007, we tested nasopharyngeal aspiration specimens in children hospitalized with ALRTI with the multiplex reverse transcriptase-polymerase chain reaction to identify 6 kinds of common pathogen (hMPV, RSV, PIV, IFV A/ B, and ADV). We analyzed positive rates and clinical features by retrospective chart review.

We detected 38 (8.4%) hMPV-positive cases out of 193 (41.8%) virus-positive specimens among 462 patients. HMPV infection prevailed from March to June with incidence peaking in April. HMPV-positive patients were aged 1-5 years (76.3%), and the ratio of boys to girls was 1.2:1. The median age was 27 months. HMPV primarily caused pneumonia (76.3%) ( P =0.018). Average hospitalization of HMPV-associated ALRTI patients was 5.8 days. In addition, they showed parahilar peribronchial infiltration (100%) on chest X-ray, normal white blood cell count (73.7%), and negative C-reactive protein (86.8%) ( P >0.05). All hMPV-positive patients recovered without complication.

HMPV is a common pathogen of ALRTI in Korean children, especially in 1-5 year olds, from March to May. Immunocompetent children diagnosed with hMPV-associated ALRTI may have a good prognosis.