Influenza A virus subtype H9N2 (A/H9N2) is a subtype of the species

Influenza A virus ''Influenza A virus'' (''IAV'') causes influenza in birds and some mammals, and is the only species of the genus ''Alphainfluenzavirus'' of the virus family ''Orthomyxoviridae''. Strain (biology)#Microbiology or virology, Strains of all subtypes ...

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bird flu "Bird Flu" is an urumee melam-dance song by recording artist M.I.A. on her second studio album '' Kala'' (2007). It was released as a digital download in 2006 through XL Recordings under exclusive license to Interscope Records in the US. Cr ...

virus). Since 1998 a total of 86 cases of human infection with H9N2 viruses have been reported.

Infection in birds

H9N2 is the most common subtype of influenza viruses in Chinese chickens and thus causes great economic loss for the poultry industry, even under the long-term vaccination programs. Recent human infections with avian influenza virus revealed that H9N2 is the gene donor for

H7N9 Influenza A virus subtype H7N9 (A/H7N9) is a bird flu strain of the species Influenza virus A (avian influenza virus or bird flu virus). Avian influenza A H7 viruses normally circulate amongst avian populations with some variants known to occ ...

and

H10N8 H1, H-1, H01, H I may refer to: Places *Interstate H-1, a highway in Hawaii * Area H1, the area of Hebron controlled by the Palestinian Authority under the Hebron Protocol Science * H1 (particle detector) * Histamine H1 receptor * Histone H1, ...

viruses that are infecting humans too. The crucial role of H9N2 viruses due to the wide host range, adaptation to both poultry and mammals and extensive gene reassortment. In China, which is regarded as a breeding ground of avian influenza viruses, the H9N2 virus has been detected in multiple avian species, including

chicken The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adult m ...

duck Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a form t ...

quail Quail is a collective name for several genera of mid-sized birds generally placed in the order Galliformes. The collective noun for a group of quail is a flock, covey, or bevy. Old World quail are placed in the family Phasianidae, and New Wor ...

pheasant Pheasants ( ) are birds of several genera within the family (biology), family Phasianidae in the order (biology), order Galliformes. Although they can be found all over the world in introduced (and captive) populations, the pheasant genera na ...

partridge A partridge is a medium-sized Galliformes, galliform bird in any of several genera, with a wide Indigenous (ecology), native distribution throughout parts of Europe, Asia and Africa. Several species have been introduced to the Americas. They a ...

pigeon Columbidae () is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with short necks and short slender bills that in some species feature fleshy ceres. They primarily ...

, silky chicken, chukar and

egret Egrets ( ) are herons, generally long-legged wading birds, that have white or buff plumage, developing fine plumes (usually milky white) during the breeding season. Egrets are not a biologically distinct group from herons and have the same build ...

. Epidemiological and genetic studies revealed that the hemagglutinin (HA) gene of the H9N2 influenza viruses could be divided into Eurasian avian and American avian lineages. The Eurasian avian lineage involved three distinct lineages, including A/chicken/Beijing/1/94-like (BJ/94-like), A/quail/Hong Kong/G1/97-like (G1-like), and A/duck/Hong Kong/Y439/97 (Y439-like).

Transmission from chicken to human

The H9N2 influenza virus can be transmitted by air droplet, dust, feed, or water.

Chickens The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adult m ...

usually seemed to be healthy after the infection but some of them do show depression and ruffled feathers. The

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

replicates itself in the trachea. It makes chickens more susceptible to secondary infections, especially ''

Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...

'' infections with a mortality rate of at least 10%. Also, the trachea or bronchi are easily embolized by mucus when the ventilation is poor, leading to severe respiratory disease and death.

Antigenicity

H9N2 viruses isolated from chickens in China showed antigenic drift that evolved into distinct antigenic groups. This antigenic drift may have led to immunization failure and may explain the current prevalence of the H9N2 influenza virus in China. The identification of amino acids in H9 antigenic sites revealed different distribution of antigenic areas among other subtypes. Multiple amino acid positions in HA protein related to the antigenicity of H9N2 viruses were identified, most of which located in the distal head of the HA trimer. H9N2 influenza virus has been recognized to reassort with multiple other subtypes, including H6N1, H6N2, and

H5N1 Influenza A virus subtype H5N1 (A/H5N1) is a subtype of the influenza A virus which can cause illness in humans and many other animal species. A bird-adapted strain of H5N1, called HPAI A(H5N1) for highly pathogenic avian influenza virus of typ ...

viruses. Moreover,

influenza viruses continued to reassort with circulating H9N2 viruses, resulting in multiple genotypes of

viruses. The contribution of H9N2 genes, especially ribonucleoprotein (RNP) genes, to the infection in human needs to be determined.

Sources

External links

Influenza Research Database
Database of influenza genomic sequences and related information. {{Taxonbar, from=Q3124723

H9N2 Influenza A virus subtype H9N2 (A/H9N2) is a subtype of the species Influenza A virus ( bird flu virus). Since 1998 a total of 86 cases of human infection with H9N2 viruses have been reported. Infection in birds H9N2 is the most common subtype ...

Infection in birds

Transmission from chicken to human

Antigenicity

Sources

Further reading

External links