Metapneumovirus
| Metapneumovirus | |
|---|---|
| Virus classification | |
| Group: | Group V ((−)ssRNA) |
| Order: | Mononegavirales |
| Family: | Pneumoviridae |
| Genus: | Metapneumovirus |
| Type species | |
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Avian metapneumovirus |
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| Species | |
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Human metapneumovirus (HMPV) is a negative single-stranded RNA virus of the family Pneumoviridae and is closely related to the avian metapneumovirus (AMPV) subgroup C. It was isolated for the first time in 2001 in the Netherlands by using the RAP-PCR (RNA arbitrarily primed PCR) technique for identification of unknown viruses growing in cultured cells. It may be the second most common cause (after the human respiratory syncytial virus) of lower respiratory infection in young children.
Compared with respiratory syncytial virus, infection with human metapneumovirus tends to occur in slightly older children and to produce disease that is less severe. Co-infection with both viruses can occur, and is generally associated with worse disease.
Table legend: "*" denotes type species.
Human metapneumovirus accounts for approximately 10% of respiratory tract infections that are not related to previously known causes. The virus seems to be distributed worldwide and to have a seasonal distribution with its incidence comparable to that for the influenza viruses during winter. Serologic studies have shown that by the age of five, virtually all children have been exposed to the virus and reinfections appear to be common. Human metapneumovirus may cause mild respiratory tract infection. However, small children, elderly and immunocompromised individuals are at risk of severe disease and hospitalization.
The genomic organisation of HMPV is analogous to HRSV, however HMPV lacks the non-structural genes, NS1 and NS2, and the HMPV antisense RNA genome contains eight open reading frames in slightly different gene order than RSV (viz. 3’-N-P-M-F-M2-SH-G-L-5’). HMPV is genetically similar to the avian metapneumoviruses A, B and in particular type C. Phylogenetic analysis of HMPV has demonstrated the existence of two main genetic lineages termed subtype A and B containing within them the subgroups A1/A2 and B1/B2 respectively.
The identification of HMPV has predominantly relied on reverse-transcriptase polymerase chain reaction (RT-PCR) technology to amplify directly from RNA extracted from respiratory specimens. Alternative more cost-effective approaches to the detection of HMPV by nucleic acid-based approaches have been employed and these include:
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