Genotype Variability and Clinical Features of Human Metapneumovirus Isolated from Korean Children, 2007 to 2010

This study was undertaken to determine the genotype variability of human metapneumovirus (hMPV) and its circulation pattern over a 3.5-year period, and to evaluate its clinical characteristics in Korean children. We investigated 4599 pediatric patients who were referred for a routine respiratory virus test by RT-PCR. hMPV genotype analyses were performed using a nested PCR-restriction fragment length polymorphism assay. Clinical and laboratory data obtained from medical records were reviewed retrospectively. Of the 4599 samples tested, 325 (7.1%) were positive for hMPV, and the co-infection rate among these 325 was 16%. Nested PCR-restriction fragment length polymorphism analysis clearly identified four of the five hMPV genotypes (A2a, A2b, B1, and B2) in 97.8%. The predominant genotype of hMPV changed over the 3.5-year study period from genotype A2a to B2 and then back to A2a. The most common genotype was A2a (214/325, 65.8%). Evidence of recurrent infection was obtained in one child only. Lymphocytosis was more frequent in children with a co-infection, but sputum production was less frequent than in children with a single infection. In genotype A2a hMPV-infected children, sneezing and neutrophilia were more frequent than in genotype B1 or B2 hMPV-infected children. This study broadens knowledge regarding the prevalence, the seasonal incidence, the occurrences of co-infection and re-infection, and the genotype diversity of hMPV in Korea.