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DRAFT MATERIAL
[[File:Main international flyways - bird migration-fr.svg|thumb|400px|The eight major flyways used by shorebirds (waders) on migration

{{Legend|#54A1FF|Pacific}} {{Legend|#EEDCD0|Mississippi}} {{Legend|#EAD27A|West Atlantic}} {{Legend|#CDDBC3|East Atlantic}} {{Legend|#ff187a|Mediterranean and Black Sea}} {{Legend|#D7C6D9|West Asia and Africa}} {{Legend|#FFC6C6|Central Asia and India}} {{Legend|#53F05A|East Asia and Australasia}} ]]

Compiled version of lead
H?N? is a subtype of the influenza A virus, which causes influenza (flu).

H5N2
H5 N2 is a subtype of the species Influenzavirus A (avian influenza virus or bird flu virus). The subtype infects a wide variety of birds, including chickens, ducks, turkeys, falcons, and ostriches. Affected birds usually do not appear ill, and the disease is often mild as avian influenza viral subtypes go. Some variants of the subtype are much more pathogenic than others, and outbreaks of "high-path" H5N2 result in the culling of thousands of birds in poultry farms from time to time. It appears that people who work with birds can be infected by the virus, but suffer hardly any noticeable health effects. Even people exposed to the highly pathogenic H5N2 variety that killed ostrich chicks in South Africa only seem to have developed conjunctivitis, or a perhaps a mild respiratory illness. There is no evidence of human-to-human spread of H5N2. On November 12, 2005 it was reported that a falcon was found to have H5N2. On June 5, 2024, the first confirmed human case of H5N2 was reported in Mexico.

H5N1
Influenza A virus subtype H5N1 (A/H5N1) is a subtype of the influenza A virus, which causes influenza (flu), predominantly in birds. It is enzootic (maintained in the population) in many bird populations, and also panzootic (affecting animals of many species over a wide area). A/H5N1 virus can also infect mammals (including humans) that have been exposed to infected birds; in these cases, symptoms are frequently severe or fatal.

H1N1
In virology, influenza A virus subtype H1N1 (A/H1N1) is a subtype of influenza A virus. Major outbreaks of H1N1 strains in humans include the 1918 Spanish flu pandemic, the 1977 Russian flu pandemic and the 2009 swine flu pandemic. It is an orthomyxovirus that contains the glycoproteins hemagglutinin (H) and neuraminidase (N), antigens whose subtypes are used to classify the strains of the virus as H1N1, H1N2 etc. Hemagglutinin causes red blood cells to clump together and binds the virus to the infected cell. Neuraminidase is a type of glycoside hydrolase enzyme which helps to move the virus particles through the infected cell and assist in budding from the host cells.

Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza, for instance in 2004–2005. Other strains of H1N1 are endemic in pigs (swine influenza) and in birds (avian influenza). Its size is 80 to 120 nm in diameter.

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.

H3N2
Influenza A virus subtype H3N2 (A/H3N2) is a subtype of viruses that causes influenza (flu). H3N2 viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains. In years in which H3N2 is the predominant strain, there are more hospitalizations.

H2N2
Influenza A virus subtype H2N2 (A/H2N2) is a subtype of Influenza A virus. H2N2 has mutated into various strains including the "Asian flu" strain (now extinct in the wild), H3N2, and various strains found in birds. It is also suspected of causing a human pandemic in 1889. The geographic spreading of the 1889 Russian flu has been studied and published.

H5N6
H5N6 is a subtype of the species Influenza A virus (sometimes called bird flu virus). Infected birds shed the virus in their saliva, mucous, and feces. The virus was first detected in poultry in 2013, since then spreading among wild bird populations and poultry around the world. Humans can be infected through unprotected contact with infected birds or contaminated surfaces. The virus transmits by getting into a person's eyes, nose, mouth, and through inhalation. Human infections are rare. Since 2014, at least 87 cases have occurred in humans. 29 people have died. A spike in human cases was reported in 2021. There have been no confirmed cases of human-to-human transmission. Some infections have been identified where no direct contact with infected birds or contaminated surfaces has been known to had occurred. Only one infected woman has said that she never came into any contact with poultry.

H5N8
H5N8 is a subtype of the influenza A virus (sometimes called bird flu) and is highly lethal to wild birds and poultry. H5N8 is typically not associated with humans. However, seven people in Russia were found to be infected in 2021, becoming the first documented human cases.

H1N2
Influenza A virus subtype H1N2 (A/H1N2) is a subtype of the species Influenza A virus (sometimes called bird flu or swine flu). It is currently endemic in pig populations and is occasionally seen in humans. The virus does not cause more severe illness than other influenza viruses, and no unusual increases in influenza activity have been associated with it.

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Highly Pathogenic Avian Influenza (keep & copy as required)
Because of the impact of avian influenza on economically important chicken farms, a classification system was devised in 1981 which divided avian virus strains as either highly pathogenic (and therefore potentially requiring vigorous control measures) or low pathogenic. The test for this is based solely on the effect on chickens - a virus strain is highly pathogenic avian influenza (HPAI) if 75% or more of chickens die after being deliberately infected with it. The alternative classification is low pathogenic avian influenza (LPAI). This classification system has since been modified to take into account the structure of the virus' haemagglutinin protein. Other species of birds, especially water birds, can become infected with HPAI virus without experiencing severe symptoms and can spread the infection over large distances; the exact symptoms depend on the species of bird and the strain of virus. Classification of an avian virus strain as HPAI or LPAI does not predict how serious the disease might be if it infects humans or other mammals.

Influenza virus nomenclature (keep & copy as required)
To unambiguously describe a specific isolate of virus, researchers use the internationally accepted Influenza virus nomenclature, which describes, among other things, the species of animal from which the virus was isolated, and the place and year of collection. As an example - A/chicken/Nakorn-Patom/Thailand/CU-K2/04(H5N1):


 * A stands for the genus of influenza (A, B or C).
 * chicken is the animal species the isolate was found in (note: human isolates lack this component term and are thus identified as human isolates by default)
 * Nakorn-Patom/Thailand is the place this specific virus was isolated
 * CU-K2 is the laboratory reference number that identifies it from other influenza viruses isolated at the same place and year
 * 04 represents the year of isolation 2004
 * H5 stands for the fifth of several known types of the protein hemagglutinin.
 * N1 stands for the first of several known types of the protein neuraminidase.

Other examples include: A/duck/Hong Kong/308/78(H5N3), A/avian/NY/01(H5N2), A/chicken/Mexico/31381-3/94(H5N2), and A/shoveler/Egypt/03(H5N2).

Research (keep & copy as required)
Influenza research includes efforts to understand how influenza viruses enter hosts, the relationship between influenza viruses and bacteria, how influenza symptoms progress, and why some influenza viruses are deadlier than others. Past pandemics, and especially the 1918 pandemic, are the subject of much research to understand flu pandemics.

The World Health Organization has published a Research Agenda with five streams:


 * Stream 1. Reducing the risk of emergence of pandemic influenza. This stream is entirely focused on preventing and limiting pandemic influenza; this includes research into what characteristics make a strain either mild or deadly, worldwide surveillance of influenza A viruses with pandemic potential, and the prevention and management of potentially zoonotic influenza in domestic and farmed animals.
 * Stream 2. Limiting the spread of pandemic, zoonotic and seasonal epidemic influenza. This is more broadly targeted at both pandemic and seasonal influenza, looking at the transmission of the virus between people and the ways in which it can spread globally, as well as the environmental and social factors which affect transmission.
 * Stream 3. Minimizing the impact of pandemic, zoonotic, and seasonal epidemic influenza. This is principally concerned with vaccination - improving the effectiveness of vaccines, vaccine technology, as well as the speed with which an effective vaccine can be developed and ways in which vaccines can be manufactured and delivered worldwide.
 * Stream 4. Optimizing the treatment of patients. This stream aims to reduce the impact of influenza by looking at methods of treatment, vulnerable groups, genetic predispositions, the interaction of influenza infection with other diseases, and influenza sequelae.
 * Stream 5. Promoting the development and application of modern public health tools. Aiming to improve the ways in which public policy can combat influenza; this includes the introduction of new technologies, epidemic and pandemic modelling, and the communication of accurate and trustworthy information to the public.