Hospitalizations for human metapneumovirus jump

Hospitalizations for human metapneumovirus (HMPV) in children aged younger than 5 years has reached an annual rate similar to that of influenza, according to a study of the disease burden of the respiratory illness in young patients.

Researchers conducted prospective surveillance for acute respiratory illness or fever among inpatient and outpatient preschool-aged children in 3 US counties from 2003 through 2009. They collected clinical and demographic data from parents and medical records and detected HMPV through reverse-transcriptase polymerase-chain-reaction assay.

They identified HMPV in 200 of 3,490 hospitalized children, 222 of 3,257 children in outpatient clinics, 224 of 3,001 children in emergency departments (EDs), and in 10 of 770 asymptomatic controls, for rates of 6% in inpatients, 7% in outpatients, and 1% in the controls.

Children infected with HMPV were more likely to be diagnosed with pneumonia, bronchiolitis, or asthma; require supplemental oxygen; undergo chest radiography; and stay longer in pediatric intensive care than those hospitalized patients without it. Outpatients generally were diagnosed with viral illness or bronchiolitis.

The findings show that for children aged younger than 5 years, the annual rate of hospitalization associated with HMPV was 1 in 1,000, the same as the rate for influenza and parainfluenza viruses but lower than the rate for respiratory syncytial virus of 3 per 1,000. Extrapolating the rates suggests that 20,000 hospitalizations associated with HMPV infection occur annually in this age group.

The estimated annual burden of outpatient visits associated with HMPV was 55 clinic visits and 23 ED visits per 1,000 children. Extrapolating the annual rates suggests that 1 million outpatient clinic visits and 263,000 ED visits may be associated with HMPV.

The researchers caution that detecting the HMPV virus does not prove causation of the illness. Year-round community surveillance will help to define peak clusters of HMPV activity and specific diagnostic methods will differentiate the virus from other acute respiratory illnesses in young children.