Epidemiology of human metapneumovirus

Abstract

Since the discovery of human metapneumovirus (hMPV) in 2001, the virus has been identified worldwide. hMPV is a common respiratory pathogen, particularly in infants and young children. The virus is associated with both upper and lower respiratory tract infections and may be a trigger for asthma. At least two major genotypes of hMPV circulate during community outbreaks. Whether these genotypes represent distinct serotypes remains controversial. The major challenges faced by the medical and scientific communities are the understanding of the pathogenesis of hMPV disease and the development of a safe and effective vaccine to protect against infection and disease caused by this newly recognized respiratory virus.

FIG. 1.

Human pathogens in the family Paramyxoviridae (data from reference 38).

FIG. 2.

Genomic maps of the Pneumovirinae. Genomic maps of the negative-sense, single-stranded RNA genomes of hMPV and RSV are displayed in the 3′-to-5′ orientation. In hMPV, the F and M2 genes are 3′ to the SH and G genes, whereas in RSV, the order of these genes is reversed. The RSV genome encodes two nonstructural proteins, NS-1 and NS-2 (shaded), that are not present in the hMPV genome. The M2 genes of both viruses carry two ORFs (M2-1 and M2-2) (not shown). The M2 and L genes overlap in the RSV genome (triangle). The L gene of each virus, encoding the viral RNA-dependent RNA polymerase, comprises two-thirds of the viral genome and is shortened for figure clarity. The genomes are not drawn to scale.

FIG. 3.

Distribution of hMPV and other respiratory viruses in New Haven, Connecticut. (Top panel) Weekly distribution of hMPV genotypes from 1 November 2001 to 31 October 2002. Genotype assignments are indicated. Every other week is marked for figure clarity. There are a total of 54 hMPV-positive samples. (Bottom panel) Monthly distribution of hMPV, RSV, influenza A and B viruses, and human parainfluenza viruses 1 to 3. The percentage of total positive specimens for each virus during the 1-year period is indicated. (Reprinted from reference with permission. © 2004 by the Infectious Diseases Society of America. All rights reserved.)

FIG. 4.

Phylogenetic analysis of hMPV. Sequences of the hMPV F genes from isolates originating from Connecticut, The Netherlands, Australia, and Canada were used to construct a phylogenetic tree. Bootstrap values are displayed at major branch points. A representative set of Connecticut sequences is displayed. Genotypes are labeled group A and group B as originally proposed in reference . NL/1/00 is a prototype group A strain, and CAN 98-75 is a prototype B strain. The dashed line separates group A and B viruses. (Modified [to reflect the current terminology] from reference with permission. © 2004 by the Infectious Diseases Society of America. All rights reserved.)

FIG. 5.

Seroepidemiology of hMPV. The percentage of hMPV seropositivity and the number of serum samples (n) for each age group are indicated. Error bars represent 95% confidence intervals. (Reprinted from reference .)