Human metapneumovirus (hMPV) was first described by van den Hoogen et al in 2001.[1] It had been isolated from young children with respiratory tract disease, and studies of old serum samples found that hMPV had been present in the European community for more than 60 years.
The presence of hMPV was soon reported in the Australian paediatric population [2] and subsequently found worldwide. The literature indicates that HMPV is among many endemic and global human respiratory viruses.
HMPV infection can result in signs and symptoms of acute respiratory tract infection (ARTI or ARI) that are indistinguishable from those of other common respiratory viruses. The proportion of ARTI cases that test positive for HMPV is not particularly informative for HMPV because it varies widely by time of year, test method, and population type.
An infected individual may remain asymptomatic or show clinical features including rhinorrhoea, cough, shortness of breath, wheeze, vomiting, pharyngitis, chest wheeze with crackles, bilateral lung cellular infiltrates and bronchiolitis. HMPV has been considered a causative agent of wheezing.[8]
HMPV is a member of the order Mononegavirales (single strand of negative-sense genetic material) family Pneumoviridae, genus Metapneumovirus, species Metapneumovirus hominis.[5] HMPV contains a single-stranded, negative-sense RNA (-ssRNA) genome of 13,300 nucleotides that includes 8 genes encoding 9 proteins, which are called (gene name; function):
- Nucleoprotein (N; replication)
- Phosphoprotein (P; replication)
- Matrix (M; structure; envelope protein)
- Fusion (F; structure; envelope protein)
- Matrix 2 (M2-1 and M2-2; structure)
- Small hydrophobic (SH; structure; envelope protein)
- Glycoprotein (G; structure)
- Large RNA-dependent RNA polymerase (L; replication)
Neighbor-Joining tree, drawn to scale
using MEGA v6; 500 bootstraps.
The closest genetic relative remains the avian pneumovirus (APV).[6] HMPV variants belong to two genetic lineages, A and B. The lineages appear to be distinct serotypes.[6] Four main sublineages were identified: A1, A2, B1 and B2.[3,4] The A1 sublineage of viruses hasn’t been detected in hospital or general practitioner clinic samples since 2006 in the Netherlands.[6,7]
As expected of RNA viruses, the remaining viruses continue to evolve and are ascribed letters such as A2a and A2b or numbers such as A2.1 or A2.2, depending on the author.[7] A more structured nomenclature was recently suggested for each variant: HMPV/country/isolate number/year/lineage, with a preference for the proposed numerical system.[7] While F gene sequencing can be used as a robust lineage-typing tool, a full genomic sequence better captures changes, such as a duplication of sequences within the G gene that emerged in 2014.[7]
HMPV’s genetic material is RNA, wrapped in a protein, which, together with other components, is contained within a lipid envelope. The exceptions are the viral proteins that protrude from the envelope. HMPV RNA has been detected in large and small droplets expelled from infected individuals.[4]
As with any respiratory virus, containing its spread is difficult once it has become established in healthcare settings, homes or other close-quarter environments.
Stephen B. (2009). Epidemiology. In Ronald Eccles and Olaf Weber (Ed.), Common Cold
(pp. 77-106). Basel, Switzerland: Birkhäuser Basel.
doi:10.1007/978-3-7643-9912-2_4.
HMPV causes initial disease in a similar age group to respiratory syncytial virus (RSV; a well-known childhood respiratory virus pathogen)- children are infected with hMPV by five years of age.[ Most of the time, these infections do not cause severe disease. In addition, the virus can severely affect older people [9] and immunocompromised individuals.
HMPV infections peak seasonally in temperate climates. The spring and autumn periods tend to show more activity, but the virus can circulate year-round, as is the case for all respiratory viruses.
References
- A newly discovered human pneumovirus isolated from young children with respiratory tract disease.
http://www.nature.com/index.html?file=/nm/journal/v7/n6/abs/nm0601_719.html&dynoptions=doi1020034962 - Evidence of human metapneumovirus in Australian children.
https://www.mja.com.au/journal/2002/176/4/evidence-human-metapneumovirus-australian-children - Antigenic and genetic variability of human metapneumoviruses.
http://www.ncbi.nlm.nih.gov/pubmed/15200856 - Respiratory virus RNA is detectable in airborne and droplet particles.
http://www.ncbi.nlm.nih.gov/pubmed/23959825 - http://www.ictvonline.org/virusTaxonomy.asp
- Zoonotic Origins of Human Metapneumovirus: A Journey from Birds to Humans.
Jesse ST, Ludlow M, Osterhaus ADME
https://www.mdpi.com/1999-4915/14/4/677 - Emergence and Potential Extinction of Genetic Lineages of Human Metapneumovirus between 2005 and 2021.
https://journals.asm.org/doi/epub/10.1128/mbio.02280-22 - Metapneumovirus and acute wheezing in children.
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(02)11391-2/fulltext - The Silent Threat of Human Metapneumovirus: Clinical Challenges and Diagnostic Insights from a Severe Pneumonia Case.
https://www.mdpi.com/2076-2607/13/1/73
*Imported Post
- This post from 26JAN2016 was originally published on my old blog platform, virologydownunder.blogspot.com.au. It has now been moved here.
- 26JAN2026 – light editing for grammar.
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