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ABSTRACT & COMMENTARY

Burden of Human Metapneumovirus Infection in Young Children

March 1, 2013
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By Joseph F John, Jr., MD, FACP, FIDSA, FSHEA, Associate Chief of Staff for Education, Ralph H. Johnson Veterans Administration Medical Center; Professor of Medicine, Medical University of South Carolina, Charleston, is Editor for Infectious Disease Alert.

Dr. John reports no financial relationships with this field of study.

Synopsis: Over a period of six years, three sites studied the prevalence of Human metapneumovirus (HMPV) in children less than 5 years old. Over the course of the study 12,363 symptomatic children were enrolled. Of 3,490 hospitalized children, 200 had evidence of HMPV infection, with the majority of these children being previously healthy.

Source: Edwards KM, et al. Burden of human metapneumovirus infection in young children. New Eng J Med 2013 368:633-43.

Human metapneumovirus (HMPV) was only discovered about a decade ago and until this study the extent of the disease — particularly in the young — was not known. Over a six year period, three sites (Cincinnati, Nashville, Rochester, NY) studied the prevalence in children less than 5 years old. At the three sites symptomatic and non-symptomatic control children had nasal and throat swabs analyzed by RT-PCR that amplified a piece of the HMPV. Over the course of the study 12,363 symptomatic children were enrolled. Of 3490 hospitalized children, 200 had evidence of HMPV infection, with the majority of these children being previously healthy. That translates to about 20,000 children a year who are hospitalized with this virus.

HMPV as compared to non-HMPV disease acted like many of the viruses that produce severe respiratory infection in children and in adults. However, in this study HMPV was more likely to produce a disease that required ICU stay, had a diagnosis of pneumonia or asthma, and needed oxygen supplementation. Other outcomes like hospital length of stay were the same for HMPV and other respiratory viruses. Both boys and girls had the same rate of hospitalization. The actual rate of hospitalization was 1 per 1000 children for HMPV, lower than that for respiratory syncytial virus (RSV) but the same as influenza. The rate of HMPV infection was 55 per 1000 clinic visits. There were no deaths in the study cohort, as well as in those children with influenza or RSV.

Commentary

Since 2000 we have seen the emergence of a number of newly recognized pathogens. New coronaviruses after SARS have emerged. New influenza viruses have caused human infection and death. Hantavirus continues to evolve. Since the HMPV discovery a decade ago, we have seen the quilt of HMPV being pieced together: A respiratory pathogen that caused a spectrum of respiratory disease in young children including pneumonia that requires hospitalization. One of the authors of this paper, Carolyn Breeze Hall — in seminal papers published on RSV over 30 years ago — uncovered an RSV story that sounds much like the one of HMPV today. It was first recognized as a new respiratory pathogen capable of causing serious illness and even requiring ICU admission. A sad footnote on this paper was the fact that Dr. Hall is recently deceased, a great loss to our infectious diseases community. Her work with others at the University of Rochester, has allowed us to compare a sizeable RSV epidemiology database to that for emerging HMPV. Specifically in the current paper, HMPV probably causes more frank pneumonia than bronchiolitis. The current study also warns us that HMPV’s epidemiology, while resembling RSV of the early days of clinical investigation, looms as an adult pathogen that I predict we will recognize with more study.

Where do we go from here with HMPV? We need more epidemiologic studies from across the world. We need to know the molecular variation the virus manifests. We need more data of how often other respiratory pathogens act with HMPV to cause disease in children and adults. Finally we need serious, supported funding to find antiviral medications that can limit or cure these infections. Such antiviral agents would not be orphan drugs, but will not garner huge profits for pharmaceutical companies. Still, like the early antibiotics, they will bring true and needed relief from pain and suffering for children and their families due to the severe illness caused by these respiratory viruses.