[Surveillance on human metapneumovirus in infants and children with acute respiratory infections in Beijing, from 2004 to 2006].

OBJECTIVE

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

METHODS

Gene 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.

RESULTS

Out 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.

CONCLUSION

Our 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.