Clinical characteristics of bronchiolitis caused by human metapneumovirus in infants / 中华儿科杂志

<p><b>OBJECTIVE</b>The fact that the acute lower respiratory infections (ALRI) are associated with a newly discovered virus, human metapneumovirus (hMPV), has been shown in several studies. The authors conducted this study to understand the etiological and clinical characteristics of bronchiolitis, one of the most common ALRI in infants, caused by hMPV.</p><p><b>METHODS</b>Nasopharyngeal aspirate specimens from 54 out of 126 infants with bronchiolitis admitted to the Children's Hospital Affiliated to Capital Institute of Pediatrics, Beijing from November 2002 to February 2003 were examined for hMPV gene fragments by reverse transcription-polymerase chain reaction (RT-PCR). Prior to the detection, the specimens were confirmed as negative for the common respiratory pathogens including RSV, influenza A and B, parainfluenza I, II, III, adenovirus, Mycoplasma pneumoniae by indirect immunofluorescence test, virus isolation and ELISA test. The clinical data of the patients diagnosed etiologically as hMPV infection analyzed included the infants' age, sex, the degree of fever, the severity of wheezing and clinical Lowell score, the findings of chest examination and chest X-ray, the white blood cell count and blood gas analysis, the course of the disease, the major treatments and the outcome of the disease.</p><p><b>RESULTS</b>Twenty-one specimens showed the predicted 213 bp PCR products in agarose gel and the positive rate was 16.7% of all patients (21/126) and 39% of the patients with negative results for common respiratory pathogens detections (21/54). The range of patients' age was 2 - 15 months and the young infants with hMPV bronchiolitis (1 - 6 month of age) accounted for 62% and the male:female ratio was 3.2:1. The patients presented a low-medium grade fever (T < 39 degrees C) accounted for 86%; 81.0% of patients had a white blood cell count lower than 10.0 x 10(9)/L. The radiological findings were patchey opacity in both lungs (68%) and(or) hyperinflation (62%). Assessed by the Lowell score system, 5 out of 21 cases were considered as severe cases. The major clinical findings of hMPV bronchiolitis had no significant difference compared with that of subgroup A hRSV bronchiolitis, and showed longer course of disease than that of subgroup B hRSV bronchiolitis (P < 0.01).</p><p><b>CONCLUSIONS</b>Of the infants with bronchiolitis hospitalized in our hospital from November of 2002 through February of 2003, 16.7% were caused by hMPV infection. These data showed that the major clinical characteristics and the outcome of treatment of hMPV bronchiolitis had no statistically significant difference compared to the cases with either subgroup A or subgroup B hRSV infection.</p>

Human metapneumovirus may associate with acute respiratory infections in hospitalized pediatric patients in Beijing, China / 中华儿科杂志

<p><b>OBJECTIVE</b>A new respiratory virus, human metapneumovirus (HMPV) was recently identified by scientists in the Netherlands first and then in a few other countries. To investigate if this newly discovered virus is associated with the acute respiratory infections in pediatric patients in Beijing, tests were developed to detect HPMV gene fragments from nasopharyngeal aspirates collected from infants and young children hospitalized for acute respiratory infections from November 2002 to March 2003.</p><p><b>METHODS</b>The HMPV was screened by reverse transcription-polymerase chain reaction (RT-PCR). RNAs were extracted by Trizol from 247 specimens which had been determined as negative for conventional respiratory viruses including RSV, influenza A and B, parainfluenza I, II, III and adenovirus by indirect immunofluorescence test as well as virus isolation. The HMPV RNAs were detected by reverse transcription tests using random primer and M-MLV reverse transcriptase followed by PCR using the primers designed from the published sequence of the N protein-encoding gene from the first HMPV identified in the Netherlands. PCR products were visualized by 1.2% agarose gel electrophoresis. Selected positive PCR products were sequenced and the sequences of the nucleotides and deduced amino acids were compared with those in the GenBank.</p><p><b>RESULTS</b>Among those 247 specimens negative for common respiratory viruses, 74 (30.0%) showed the predicted 213 bp PCR products in agarose gel. Most of clinical diagnoses for these 58 patients were pneumonia (36, 48.6%), bronchiolitis (21, 28.4%), and bronchitis and asthma in some patients. Nearly 90 percent of positive specimens were from patients under 2 years of age. Ten out of 74 amplicons were randomly selected for sequence analysis. When compared with the sequences in the GenBank, the nucleotide sequences of these 10 amplicons shared high homology only with those of HMPVs. The nucleotide sequence identities of these 10 samples with those from the Netherlands and Canada were 87% - 99%. When compared with the nucleotide sequence from the first reported strain by Van den Hoogen (strain HMPV 00-1), the sequence identities of these 10 fragments ranged from 88.7% to 99.1%. Among the 10 amplicons from the specimens, the nucleotide identities were 87.3% - 100%. One of the 10 amplicons (No. 1816) shared lower identity with others (87.3% - 89.7%), whereas the other 9 shared higher identities (95.8% - 100%) with each other. The comparison of amino acids showed that these 10 amplicons showed high homology (95.8% - 100%). Again, amplicon No.1816 shared lower homology (95.8% - 97.2%) with others, whereas the other 9 shared higher homology (98.6% - 100%). The amino acid homology between No.1816 and HMPV 00-1 was 95.8%, whereas that of the other 9 with HMPV 00-1 was 98.6% - 100%.</p><p><b>CONCLUSION</b>These data suggested that some of acute respiratory infections in pediatric patients in Beijing area are related to the newly identified human metapneumovirus. The HMPV circulating in Beijing may have different genotypes.</p>