Human Metapneumovirus Infection in Children

Abstract & Commentary

Synopsis: Human metapneumovirus was found in 6.4% of respiratory tract specimens collected from children < 5 years of age who had no evidence of other respiratory tract pathogens. Cough, rhinorrhea, and wheezing occurred in approximately two-thirds of patients, and fever occurred in half.

Source: Esper F, et al. Human metapneumovirus infection in the United States: Clinical manifestations associated with a newly emerging respiratory infection in children. Pediatrics. 2003;111:1407-1410.

Respiratory tract specimens (nasopharyngeal swabs, washes, and bronchoalveolar lavage) collected from children < 5 years of age who were negative by direct fluorescent antibody (DFA) tests for the presence of respiratory syncytial virus (RSV), influenza, parainfluenza, and adenovirus antigens were tested for the presence of human metapneumovirus (hMPV) by RT-PCR. From Oct. 30, 2001, to Feb. 28, 2002, 357 specimens from 296 children were tested. From these, hMPV was detected in 16 (5.4%) children who had no evidence of co-infection with another respiratory tract pathogen.

Clinical information was obtained by chart review. The most common clinical findings of hMPV infection were cough (11 of 16 [69%]), rhinorrhea (11 of 16 [69%]), fever (10 of 16 [63%]), and wheezing (8 of 16 [50%]). Five patients (31%) developed hypoxia (oxygen saturation of < 90%). Chest radiographs were obtained from 14 children, which showed abnormal findings including peribronchial cuffing, prominent hilum, and focal infiltrates. All hMPV infections occurred during a 6-week period in January and February 2002, although only 59% of specimens were from this period. No hMPV was detected in isolates obtained in November or December 2001.

Comment by Hal B. Jenson, MD

The prevalence of hMPV is unknown, but hMPV has been found in Great Britain, Australia, Hong Kong, and Canada. This study shows that, during the winter of 2001, hMPV was present in the United States and accounted for approximately 5% of respiratory illnesses not caused by RSV, influenza viruses, parainfluenza viruses, or adenoviruses among children < 5 years of age. The detection of hMPV during a confined 6-week span during the 4-month study period strongly suggests a seasonal pattern. Additional studies incorporating active surveillance are necessary to define the epidemiology of hMPV in the general population, including the presence and transmission of hMPV among asymptomatic children and adults.

The clinical manifestations reported in this study and others reflect a wide spectrum of disease in children, with both upper and lower respiratory tract symptoms. Common diagnoses in hospitalized children with hMPV infection include pneumonia, asthma exacerbation, and acute bronchiolitis. In addition to the 16 cases with hMPV infection alone, this study reported 2 cases of co-infection, with influenza A, and 1 case of nosocomial infection. Co-infection may contribute to the severity of clinical illness. The possibility of nosocomial transmission underscores the need for developing sensitive diagnostic tests for hMPV.

Dr. Jenson is Chair, Department of Pediatrics, Director, Center for Pediatric Research, Eastern Virginia Medical School and Children's Hospital of the King's Daughters, Norfolk, VA.