Methods: We performed realtime RT-PCR with nasopharyngeal samples of 2,403 children who were hospitalized with acute respiratory infection. Then medical records of 120 children, who were diagnosed with hMPV respiratory infection between 2011 and 2014, were analyzed retrospectively and compared to the epidemiologic data on the respiratory virus infection reported by 'Korea Centers for Disease Control and Prevention'.
Results: We detected 120(6.9%) hMPV-positive cases out of 1723 virus-positive specimens, which prevailed mostly in Spring between March and May. The respiratory infection with hMPV was more common in female population(55%). The age distribution of hPMV infection was 7.5% in <12 month, 23.3% in 1-2 years, 26.7% in 2-3 years, 20% in 3-4 years, and 11.7% ≥5 years of age. 11.7%, showing that hPMV was prevalent among the children aged 1-4 years.
Coinfections with other respiratory viruses were observed in 34 patients (28.3%) of 120 hMPV-positive cases; rhinovirus (52.9%), adenovirus (17.6%), bocavirus (17.6%), RSV (5.9%), parainfluenza (3%) and coronavirus (3%). The outbreak of hMPV infection in 2014 was found. Among 120 hMPV-positive patients during recent 4 years, most patients (68.3%) were diagnosed in 2014, and in 2014 hMPV detection rate was 8.99% among virus-positive cases. During 2011-2014 influenza virus infection was prevalent mainly from January to March, and hMPV infection started to appear just after the end of influenza virus outbreak. In 2014, hPMV infection was mostly presented with pneumonia(81.0%), and it was more common in younger children, compared to hMPV infection in 2011-2013 (mean age; 2.04±0.84 vs 3.78±2.57, p=0.001).
Conclusions: Infection with hPMV was most prevalent among children 1-4 years of age, and hMPV was the most common causing organism of viral pneumonia during Spring season in Korean children. The hMPV infection pandemic was observed in 2014 and the clinical importance of hMPV has been increasing recently. Therefore additional studies are required to define the epidemiology, disease characteristics caused by hMPV and the cause of recent outbreak.