Elsevier

Journal of Infection

Volume 52, Issue 4, April 2006, Pages 254-263
Journal of Infection

Human metapneumovirus in infants and young children in Thailand with lower respiratory tract infections; molecular characteristics and clinical presentations

https://doi.org/10.1016/j.jinf.2005.07.001Get rights and content

Summary

Human metapneumovirus (hMPV) is a recently identified Paramyxovirus. The clinical features and molecular characteristics of hMPV in Asian populations have so far remained obscure.

Objective

The present study was designed to investigate the prevalence of hMPV in infants and young children presented with acute lower respiratory tract infection (ALRI) and to identify the molecular characteristics and clinical presentations.

Methods

There were 236 nasopharyngeal secretions (NPs) collected from infants and children presented with ALRI at King Chulalongkorn Memorial hospital between March 2001 and September 2003. Reverse transcriptase-polymerase chain reaction (RT-PCR) applying specific primers was done to identify hMPV and hRSV. Phylogenetic analysis of hMPV N, F and L genes was also performed.

Results

Of the 220 (236) infants and young children tested, positive results were found in 12 specimens (5.4%). The mean age of children with hMPV infections was 22±11 months. They mostly presented with fever with cough (100%) and upper respiratory tract symptoms (10/12, 83%). Eleven of twelve infants (92%) were hospitalized. Additionally, phylogenetic analysis identified two distinct lineages of hMPV.

Conclusion

Our results demonstrated the prevalence, molecular characterization and clinical spectrum of hMPV infection in infants and young children presented with lower respiratory tract infections in Thailand.

Introduction

Respiratory virus infections account for significant morbidity and mortality especially in young children worldwide.1, 2, 3 The viruses most frequently associated with respiratory tract infections include respiratory syncytial virus (RSV), parainfluenza viruses, adeno-virus and influenza virus.4 Due to the difficulty in distinguishing between respiratory pathogens clinically and by laboratory based analysis, studies on the impact of respiratory infections are still quite limited. Despite improved sensitivity of diagnostic techniques, the cause of a significant portion of lower respiratory tract infections has still eluded identification.5, 6, 7

In 2001, Van den Hoogens et al.8 were the first to describe a new respiratory virus, named human metapneumovirus (hMPV). It has been classified as a member of the Paramyxoviridae family, genus Pneumovirinae.8, 9 Earlier discovery of hMPV had been delayed until recently as owing to its slow growth. In addition, it has been difficult to detect in cell culture making the arrival of better molecular techniques such as RT-PCR imperative.10 This provided an opportunity to define the extent of disease caused by a previously unknown pathogen. Subsequently, hMPV was detected in several countries as for example Canada,11 France,1 Italy12 and U.S.A.13 It is likely to exist on a global scale. In Thailand, we recently identified hMPV and reported our preliminary results.14 In the present study, our aim has been to further analyse and identify the molecular characteristics of this virus in conjunction with clinical presentations, information that will prove important for future development of specific antiviral therapies and vaccines.

Section snippets

Study population

We studied nasopharyngeal secretions (NPs) obtained from infants and young children with lower respiratory tract illness attending either the outpatient clinic or admitted to King Chulalongkorn Memorial hospital between March 2001 and November 2003. The study protocol was approved by the Ethical Committee of the Faculty of Medicine, Chulalongkorn University. Parents were informed as to the study objective and their written consent was obtained before specimen collection. All the specimens were

Results

Of the 220 specimens tested, 134 had been obtained from male and 86 from female subjects, respectively. Their mean age was 13.9±11.9 months. One hundred and eighteen were positive for hRSV (54%). Twelve were positive for hMPV (5%). There were two infants co-infected with hRSV subtype B. Eleven positive specimens (91%) originated from hospitalized infants and children. All had presented with fever and cough (100%), 10 (83%) had upper respiratory tract symptoms at the time of initial examination.

Discussion

Here we describe the characterization of a novel human respiratory metapneumovirus, isolated from 12 Thai infants and children with lower respiratory tract infections (11 admitted, one OPD). The children presented mostly with clinical symptoms similar to hRSV infection, ranging from upper respiratory tract disease to acute bronchiolitis and pneumonia, which has also been stated by a recent report.19 As is the case with hRSV-infected children, young infants or those with underlying diseases

Acknowledgements

This study was supported by a grant from the Center of Excellence research fund, Chulalongkorn University and The Thailand research fund, Senior Research Scholar. We deeply appreciate Ms P. Hirsch for her critical review of this manuscript. Finally, we would like to thank the entire staff of the Department of Pediatrics at King Chulalongkorn Memorial Hospital for their tireless efforts in collecting the specimens.

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