BACKGROUNDHuman metapneumovirus (hMPV) was discovered by scientists in the Netherlands as a novel respiratory virus in 2001 and had been found in children with acute respiratory tract infections (ARTI) in China. The objective of this study was to determine the importance of hMPV infection in children in Beijing and the genotypes of the circulating virus by the surveillance during a four-consecutive-year period.

METHODSClinical specimens collected from children with ARTI from January 2006 to December 2009 were tested for hMPV by RT-PCR using primers targeting the matrix (M) gene, followed by genotyping of hMPV directly from positive samples by diplex PCR with primers for glycoprotein (G) genes. Sequence analysis was used for genotyping of those un-typable samples. Common respiratory viruses in these clinical specimens were tested by virus isolation and antigen detection, in addition to hMPV detection.

RESULTSOf 4730 tested specimens, 191 (4.0%) were positive for hMPV and 62.8% of 191 were identified as genotype A. The positive rate of hMPV from hospitalized patients was higher than that from outpatients each year. Most of hMPV positive children were under five years old. The peak of hMPV activity mostly occurred in late spring and overlapped with or followed that of respiratory syncytial virus (RSV) and followed by parainfluenza virus 3. Of hMPV infected cases, 68.6% were lower respiratory tract infection, among which 79.4% were hospitalized, and upper respiratory tract infection was diagnosed for 31.4% of hMPV infected children. The 9.4% of hMPV positive samples were found to co-exist with other respiratory viruses.

CONCLUSIONShMPV was an important pathogen for ARTI in pediatric patients, especially those under five years old. Both genotypes A and B circulated simultaneously in Beijing.

Adolescent ; China ; Female ; Genotype ; Humans ; Male ; Metapneumovirus ; genetics ; pathogenicity ; Respiratory Tract Infections ; virology ; Reverse Transcriptase Polymerase Chain Reaction

Human metapneumovirus (HMPV) shares clinical and epidemiological characteristics with well-known respiratory syncytial virus (RSV). The aim of this study was to investigate the clinical and epidemiological differences between HMPV- and RSV-induced wheezing illnesses. A total of 1,008 nasopharyngeal aspirate specimens was collected from 1,008 pediatric patients hospitalized with acute respiratory tract infection at Inje University Sanggye Paik Hospital from December 2003 to April 2008, and tested for seven common respiratory viruses. Conditions classified as wheezing illness were bronchiolitis, reactive airways disease, and bronchial asthma. HMPV caused a significantly lower proportion of wheezing illness when compared to RSV (48.1% vs. 82.2%, P<0.05). HMPV-induced wheezing illness occurred predominantly in older patients when compared to RSV patients (P<0.001). RSV infections peaked in the fall and winter followed by peaks of HMPV infection in winter and spring. Eosinophil counts were significantly higher (P<0.01) in RSV patients when compared to HMPV patients. These results show that human metapneumovirus patients exhibit several different clinical and epidemiological characteristics, such as higher proportion of wheezing illness, age and seasonal incidence, and eosinophil counts, when compared to RSV patients.
Bronchiolitis/physiopathology/virology ; Child ; Child, Preschool ; Female ; Humans ; Infant ; Korea/epidemiology ; Male ; Metapneumovirus/pathogenicity ; Nasopharynx/virology ; Paramyxoviridae Infections/*epidemiology/*physiopathology/virology ; Respiratory Sounds/*physiopathology ; Respiratory Syncytial Virus Infections/*epidemiology/*physiopathology/virology ; Respiratory Syncytial Viruses/pathogenicity ; Retrospective Studies ; Seasons

OBJECTIVETo understand the molecular epidemiologic features of human metapnenmovirus (hMPV) in children with respiratory tract infection in Hangzhou.

METHODS2 593 throat swabs were collected from patients with respiratory tract infections who visited the hospitals with sentinel surveillance programs from January 2011 to December 2013, including 1 676 outpatients and 917 inpatients. Total nucleic acid was extracted from the specimens and the fusion (F) protein gene of hMPV was amplified by quantitative real-time reverse transcription polymerase chain reaction (RT-PCR), with positive samples picked to compare with the sequence of hMPV in GenBank, after the sequence of amplification products were determined. Other two types of common respiratory virus were tested using RT-PCR.

RESULTSThe overall positive rate in this study was 6.51% (169/2 593), with 6.62% (111/1 676) in outpatients and 6.32% (58/917) in inpatients, but no statistically significant difference was found (χ(2) = 0.086, P = 0.769). The rates was 7.01% in males and 5.72% in females, with no statistically significant difference in different sex (χ(2) = 1.676, P = 0.195). The positive rate was 14.14% (28/198)in the 2-year-olds, 14.01% (22/158)in 3-year olds. The rate in 2-year olds was higher than in other groups, with statistically significant differences between the groups (χ(2) = 38.654, P = 0.000). Of the 169 positive cases, 153 (90.53%) in the younger than 5 years olds. The rates of infection with hMPV in winter and spring were statistically higher than in summer and autumn (χ(2) = 67.032, P = 0.000). The rate of co-infection was 19.52% (33/169). 88 amplified productions were selected for gene sequence analysis, and the F gene homology were 81.6%-100.0% with reference strains in GenBank. Data showed that all the 4 viral subtypes: A2 (52.27% , 46/88), B1 (37.51%, 33/88), B2 (9.09%, 8/88) and A1 (1.13%, 1/88) co-circulated during the study. However, different subtypes appeared predominant in different years:hMPV subtype B1 was in 2011 and 2012, subtype A2 in the end of 2012 and in 2013. Of the 88 specimens, gene sequences were determinate, with A genotype accounted for 67.56% (25/37), B genotype for 32.43% (12/37)in children younger than 1-year olds, and A genotype accounted for 43.13% (22/51), B genotype for 56.86% (29/51)in children above 1-year olds. Significant differences between the two groups (χ(2) = 5.143, P = 0.023) were noticed.

CONCLUSIONIt was confirmed that hMPV was one of the substantial pathogens causing the respiratory tract infections. Data from our study suggested that the peak time of hMPV infection predominated during winter and spring in Hangzhou. Both hMPV subtype B1 and subtype A2 were found popular in this study, with hMPV genotype A dominating in children younger than 1-year olds.

Child ; Child, Preschool ; China ; epidemiology ; Coinfection ; Female ; Genotype ; Humans ; Infant ; Male ; Metapneumovirus ; genetics ; pathogenicity ; Molecular Epidemiology ; Paramyxoviridae Infections ; epidemiology ; Real-Time Polymerase Chain Reaction ; Respiratory Tract Infections ; epidemiology ; Seasons ; Sentinel Surveillance

OBJECTIVETo understand the prevalence of human metapneumovirus (hMPV) infection in infants and young children in Beijing, China.

METHODSGene fragment from hMPV was amplified by reverse transcription-polymerase chain reaction (RT-PCR) with the primer pair located on the membrane (M) encoding gene. RNAs were extracted by Trizol from 3330 specimens collected from outpatients and inpatients with acute respiratory infections and visited the affiliated Children's Hospital from July 2004 to June 2006. These samples had been tested for conventional respiratory viruses including RSV, influenza A and B, parainfluenza I , II , III and adenovirus by indirect immunofluoresence assay as well as virus isolation before RT-PCR for hMPV.

RESULTSOut of the 3330 clinical samples, 110 (3.3%) were found positive to hMPV. The ratio of male to female among those positive to hMPV was 1.5:1. Fifty-one out of 110 positive (46.4%, 51/110) specimens on hMPV were from children under one year olds, 13 (11.8%,13/ 110) were from 1 to 2 year olds, 37 (33.6%, 37/110) were from 2 to 5 years of age, and 9 (8.2%, 9/110) among children over 5 years of age. hMPV was associated with: pneumonia in 44.5% (49/110) of the cases ; upper respiratory infections in 22.7% (25/110); bronchiolitis in 10.9% (12/110); and bronchitis in 7.3% (8/110). hMPV was detected almost in every month from July 2004 to June 2005 in sporadic cases whereas a peak was noticed in April 2006 during the period from July 2005 to June 2006. Among 110 positive samples, 6 (5.5%) were also positive for other viruses including 3 as Influenza B, 2 as RSV and 1 as Parainfluenza 3, suggesting that these children were co-infected with hMPV and other respiratory viruses. The peak of hMPV prevalence did not overlap with that of RSV during this period.

CONCLUSIONOur findings suggested that hMPV had been one of the important agents causing acute respiratory infections especially severe lower respiratory infections like pneumonia and bronchiolitis in pediatric patients in Beijing. Infants and young children under two years of age seemed to be more susceptible to hMPV.

Acute Disease ; Bronchiolitis ; epidemiology ; virology ; Child, Preschool ; China ; epidemiology ; Female ; Humans ; Infant ; Male ; Metapneumovirus ; classification ; genetics ; pathogenicity ; Pneumonia ; epidemiology ; virology ; Respiratory Tract Infections ; epidemiology ; virology ; Reverse Transcriptase Polymerase Chain Reaction