Understanding the socioeconomic burden of human metapneumovirus in childhood

Result

The authors of a recent Italian study have concluded that human metapneumovirus (hMPV) is a recently identified cause of acute respiratory infection in childhood and may have a significant socioeconomic impact on both children and their families. Since its first isolation in the Netherlands in 2001 , hMPV has been reported as a significant cause of respiratory tract infection, especially in the first year of life . Clinically, infection with hMPV resembles that of respiratory syncytial virus (RSV), with bronchiolitis and croup being the most commonly observed features. Previous studies reported a prevalence of hMPV in children with acute respiratory infection ranging from 4 to 20% .

The Italian study was conducted on a population of 1505 children aged < 15 years presenting to the emergency department of a single hospital in Milan between 1 November 2002 and 31 March 2003. Of the total, 1019 had symptoms of acute respiratory infection (ARI). Nasopharyngeal swabs were tested for hMPV by RT-PCR in a reference laboratory. hMPV was detected in 42 cases (4.1%) of children with ARI, RSV in 143 (14%) and influenza virus in 4.1%.

Most common symptoms of hMPV infected children were: fever >38 C (80%), wheezing (26%), pharyngitis (26%) and exacerbation of symptoms of asthma (14%). Children with hMPV infection were more likely to present with bronchiolitis or asthma exacerbation then those with influenza and more likely to have fever than those with RSV infection. Clinical outcomes were similar in the three groups, although the hospitalisation rate was slightly higher among RSV positive children. Interestingly, household contacts of hMPV positive children were more likely to develop respiratory symptoms and to seek medical attention during the 5-7 days of follow up than those of RSV-positive children.

Conclusion

Although previous studies have generally shown a higher prevalence of hMPV infection in children with ARI, the findings presented here are not surprising for several reasons: firstly, hMPV infection is more likely to occur in the first two years of life, while children included in this study were, on average, older (mean age 3.41 years, SD 3.06); secondly, a strict definition of ARI was not used and this could have led to the inclusion in the denominator of children with very mild symptoms (i.e. unlikely to be hMPV related); thirdly, data were collected from a single hospital and in only one winter season.

Acknowledgements

Study summary from: Swatee P Patel, Marjo-Riitta Järvelin and Mark P Little. Systematic review of worldwide variations of the prevalence of wheezing symptoms in children. Environmental Health 2008, 7:57.