Avian flu - AbsoluteAstronomy.com

For the H5N1 subtype of Avian influenza see Influenza A virus subtype H5N1.

Avian influenza, sometimes avian flu, and commonly bird flu, refers to "influenza

Influenza

Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...

caused by virus

Virus

A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

es adapted to bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s." Of the greatest concern is highly pathogenic avian influenza (HPAI).

"Bird flu" is a phrase similar to "swine flu

Swine flu

Swine influenza, also called pig influenza, swine flu, hog flu and pig flu, is an infection by any one of several types of swine influenza virus. Swine influenza virus or S-OIV is any strain of the influenza family of viruses that is endemic in pigs...

," "dog flu," "horse flu

Horse flu

Equine influenza is the disease caused by strains of Influenza A that are enzootic in horse species. Equine influenza occurs globally, and is caused by two main strains of virus: equine-1 and equine-2...

," or "human flu

Human flu

Human flu is a term used to refer to influenza cases caused by Orthomyxoviridae that are endemic to human populations . It is an arbitrary categorization scheme, and is not associated with phylogenetics-based taxonomy...

" in that it refers to an illness caused by any of many different strains of influenza viruses that have adapted to a specific host. All known viruses that cause influenza in birds belong to the species influenza A virus
Influenzavirus A
Influenza A virus causes influenza in birds and some mammals and is the only species of Influenzavirus A. Influenzavirus A is a genus of the Orthomyxoviridae family of viruses. Strains of all subtypes of influenza A virus have been isolated from wild birds, although disease is uncommon...

. All subtypes (but not all strains of all subtypes) of influenza A virus are adapted to birds, which is why for many purposes avian flu virus is the influenza A virus (note that the "A" does not stand for "avian").

Adaptation is not exclusive. Being adapted towards a particular species does not preclude adaptations, or partial adaptations, towards infecting different species. In this way, strains of influenza viruses are adapted to multiple species, though may be preferential towards a particular host. For example, viruses responsible for influenza pandemics are adapted to both humans and birds. Recent influenza research into the genes of the Spanish flu

Spanish flu

The 1918 flu pandemic was an influenza pandemic, and the first of the two pandemics involving H1N1 influenza virus . It was an unusually severe and deadly pandemic that spread across the world. Historical and epidemiological data are inadequate to identify the geographic origin...

virus shows it to have genes adapted to both birds and humans, with more of its genes from birds than less deadly later pandemic strains.

While its most highly pathogenic strain (H5N1) had been spreading throughout Asia since 2003, avian influenza reached Europe in 2005, and the Middle East, as well as Africa, the following year.

Genetics

Subtypes

There are many subtypes of avian influenza viruses, but only some strains of four subtypes have been highly pathogenic in humans. These are types H5N1, H7N3, H7N7 and H9N2.

Contraction/spreading of avian influenza

Most human contractions of the avian flu are a result of either handling dead infected birds or from contact with infected fluids. While most wild birds mainly have only a mild form of the H5N1 strain, once domesticated birds such as chickens or turkeys are infected, it could become much more deadly because the birds are often within close contact of one another. There is currently a large threat of this in Asia with infected poultry due to low hygiene conditions and close quarters . Although it is easy for humans to become infected from birds, it's much more difficult to do so from human to human without close and lasting contact.

Spreading of H5N1 from Asia to Europe is much more likely the cause of both legal and illegal poultry trades than dispersing through wild bird migrations, being that in recent studies, there were no secondary rises in infection in Asia when wild birds migrate south again from their breeding grounds. Instead, the infection patterns followed transportation such as railroads, roads, and country borders, suggesting poultry trade as being much more likely. While there have been strains of avian flu to exist in the United States, such as Texas in 2004, they have been extinguished and have not been known to infect humans.
Examples of avian influenza A virus strains:

HA subtype designation	NA subtype designation	Avian influenza A viruses
H1	N1	A/duck/Alberta/35/76(H1N1 H1N1 'Influenza A virus is a subtype of influenza A virus and was the most common cause of human influenza in 2009. 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. H1N1 strains caused a few percent of... )
H1	N8	A/duck/Alberta/97/77(H1N8)
H2	N9	A/duck/Germany/1/72(H2N9)
H3	N8	A/duck/Ukraine/63(H3N8 H3N8 H3N8 is a subtype of the species Influenza A virus that is endemic in birds, horses and dogs.-Introduction:Equine influenza is a highly contagious respiratorydisease of horses and related animals such as donkeys,... )
H3	N8	A/duck/England/62(H3N8 H3N8 H3N8 is a subtype of the species Influenza A virus that is endemic in birds, horses and dogs.-Introduction:Equine influenza is a highly contagious respiratorydisease of horses and related animals such as donkeys,... )
H3	N2	A/turkey/England/69(H3N2 H3N2 Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains... )
H4	N6	A/duck/Czechoslovakia/56(H4N6)
H4	N3	A/duck/Alberta/300/77(H4N3)
H5	N3	A/tern/South Africa/300/77(H4N3)
H5	N4	A/jyotichinara/Ethiopia/300/77(H6N6)
H5	N9	A/turkey/Ontario/7732/66(H5N9 H5N9 H5N9 is a subtype of the species Influenza A virus .A highly pathogenic strain of H5N9 caused a minor flu outbreak in 1966 in Ontario and Manitoba, Canada in turkeys.... )
H5	N1	A/chick/Scotland/59(H5N1 H5N1 Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species... )
H6	N2	A/turkey/Massachusetts/3740/65(H6N2 H6N2 H6N2 is an avian influenza virus with two forms: one has a low and the other a high pathogenicity. Avian derived from the Latin word avis for "bird." It can cause a serious problem for poultry.... )
H6	N8	A/turkey/Canada/63(H6N8)
H6	N5	A/shearwater/Australia/72(H6N5)
H6	N1	A/duck/Germany/1868/68(H6N1)
H7	N7	A/fowl plague virus/Dutch/27(H7N7 H7N7 H7N7 is a subtype of Influenzavirus A, a genus of Orthomyxovirus, the viruses responsible for influenza. Highly pathogenic strains and low pathogenic strains exist. H7N7 can infect humans, birds, pigs, seals, and horses in the wild; and has infected mice in laboratory studies... )
H7	N1	A/chick/Brescia/1902(H7N1 H7N1 H7N1 is a subtype of the species Influenza A virus .A highly pathogenic strain of it caused a flu outbreak with significant spread to numerous farms, resulting in great economic losses in 1999 in Italy in turkeys.... )
H7	N3	A/turkey/England/639H7N3 H7N3 H7N3 is a subtype of the species Influenza A virus .In North America, the presence of H7N3 was confirmed at several poultry farms in British Columbia in February 2004. As of April 2004, 18 farms had been quarantined to halt the spread of the virus. Two cases of humans infected with it have been... )
H7	N1	A/fowl plague virus/Rostock/34(H7N1 H7N1 H7N1 is a subtype of the species Influenza A virus .A highly pathogenic strain of it caused a flu outbreak with significant spread to numerous farms, resulting in great economic losses in 1999 in Italy in turkeys.... )
H8	N4	A/turkey/Ontario/6118/68(H8N4)
H9	N2	A/turkey/Wisconsin/1/66(H9N2 H9N2 H9N2 is a subtype of the species Influenza A virus ."H9N2 influenza viruses of domestic ducks have become established in the domestic poultry of Asia. Phylogenetic and antigenic analyses of the H9N2 viruses isolated from Hong Kong markets suggest three distinct sublineages... )
H9	N6	A/duck/Hong Kong/147/77(H9N6)
H9	N6	A/duck/Hong Kong/147/77(H9N6)
H9	N8	A/manishsurpur/Malawi/149/77(H9N8)
H9	N7	A/turkey/Scotland/70(H9N7)
H10	N8	A/quail/Italy/1117/65(H10N8)
H11	N6	A/duck/England/56(H11N6)
H11	N9	A/duck/Memphis/546/74(H11N9)
H12	N5	A/duck/Alberta/60/76/(H12N5)
H13	N6	A/gull/Maryland/704/77(H13N6)
H14	N4	A/duck/Gurjev/263/83(H14N4)
H15	N9	A/shearwater/Australia/2576/83(H15N9)

Influenza pandemic

Pandemic flu viruses have some avian flu virus genes and usually some human flu

Human flu

virus genes. Both the H2N2

H2N2

H2N2 is a subtype of the type influenzavirus A. H2N2 has mutated into various strains including the Asian flu strain , H3N2, and various strains found in birds...

and H3N2

H3N2

Influenza A virus subtype H3N2 is a subtype of viruses that cause influenza . H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains...

pandemic strains contained genes from avian influenza viruses. The new subtypes arose in pigs coinfected with avian and human viruses, and were soon transferred to humans. Swine were considered the original "intermediate host" for influenza, because they supported reassortment of divergent subtypes. However, other hosts appear capable of similar coinfection (e.g., many poultry species), and direct transmission of avian viruses to humans is possible. The Spanish flu

Spanish flu

virus strain may have been transmitted directly from birds to humans.
In spite of their pandemic connection, avian influenza viruses are noninfectious for most species. When they are infectious, they are usually asymptomatic, so the carrier does not have any disease from it. Thus, while infected with an avian flu virus, the animal does not have a "flu". Typically, when illness (called "flu") from an avian flu virus does occur, it is the result of an avian flu virus strain adapted to one species spreading to another species (usually from one bird

Bird

species to another bird species). So far as is known, the most common result of this is an illness so minor as to be not worth noticing (and thus little studied). But with the domestication of chickens and turkeys, humans have created species subtypes (domesticated poultry) that can catch an avian flu virus adapted to waterfowl and have it rapidly mutate into a form that kills over 90% of an entire flock in days, can spread to other flocks and kill 90% of them, and can only be stopped by killing every domestic bird in the area. Until H5N1

H5N1

Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species...

infected humans in the 1990s, this was the only reason avian flu was considered important. Since then, avian flu viruses have been intensively studied; resulting in changes in what is believed about flu pandemics, changes in poultry farming, changes in flu vaccination research, and changes in flu pandemic planning.

H5N1

H5N1

Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species...

has evolved into a flu virus strain that infects more species than any previously known strain, is deadlier than any previously known strain, and continues to evolve, becoming both more widespread and more deadly. This caused Robert G. Webster, a leading expert on avian flu, to publish an article titled "The world is teetering on the edge of a pandemic that could kill a large fraction of the human population" in American Scientist
American Scientist
American Scientist is the bimonthly science and technology magazine published since 1913 by Sigma Xi. Each issue includes four to five feature articles written by scientists and engineers. These authors review research in all fields of science...

. He called for adequate resources to fight what he sees as a major world threat to possibly billions of lives. Since the article was written, the world community has spent billions of dollars fighting this threat with limited success.

Vaccines have been formulated against several of the avian H5N1 influenza varieties. Vaccination of poultry against the ongoing H5N1 epizootic is widespread in certain countries. Some vaccines also exist for use in humans, and others are in testing, but none have been made available to civilian populations, nor are produced in quantities sufficient to protect more than a tiny fraction of the Earth's population in the event of an H5N1 pandemic outbreak. The World Health Organization has compiled a list of known clinical trials of pandemic influenza prototype vaccines, including those against H5N1.

H5N1

The highly pathogenic influenza A virus subtype H5N1

H5N1

Influenza A virus subtype H5N1, also known as "bird flu", A or simply H5N1, is a subtype of the influenza A virus which can cause illness in humans and many other animal species...

is an emerging avian influenza virus that has been causing global concern as a potential pandemic

Pandemic

A pandemic is an epidemic of infectious disease that is spreading through human populations across a large region; for instance multiple continents, or even worldwide. A widespread endemic disease that is stable in terms of how many people are getting sick from it is not a pandemic...

threat. It is often referred to simply as "bird flu" or "avian influenza", even though it is only one subtype of avian influenza-causing virus.

H5N1 has killed millions of poultry in a growing number of countries throughout Asia, Europe and Africa. Health experts are concerned that the coexistence of human flu viruses and avian flu viruses (especially H5N1) will provide an opportunity for genetic material to be exchanged between species-specific viruses, possibly creating a new virulent influenza strain that is easily transmissible and lethal to humans.

Since the first H5N1 outbreak occurred in 1987, there has been an increasing number of HPAI H5N1 bird-to-human transmissions, leading to clinically severe and fatal human infections. Because a significant species barrier exists between birds and humans, though, the virus does not easily cross over to humans, though some cases of infection are being researched to discern whether human to human transmission is occurring. More research is necessary to understand the pathogenesis and epidemiology of the H5N1 virus in humans. Exposure routes and other disease transmission characteristics, such as genetic and immunological factors that may increase the likelihood of infection, are not clearly understood.

On January 18, 2009, a 27-year-old woman from eastern China died of bird flu, Chinese authorities said, making her the second person to die from the deadly virus at that time. Two tests on the woman were positive for H5N1 avian influenza, said the ministry, which did not say how she might have contracted the virus.

Although millions of birds have become infected with the virus since its discovery, 306 humans have died from the H5N1 in twelve countries according to WHO

Who

Who may refer to:* Who , an English-language pronoun* who , a Unix command* Who?, one of the Five Ws in journalism- Art and entertainment :* Who? , a 1958 novel by Algis Budrys...

data as of February 2, 2011.

The avian flu claimed at least 300 humans in Azerbaijan, Cambodia, China, Egypt, Indonesia, Iraq, Laos, Nigeria, Pakistan, Thailand, Turkey, and Vietnam. Epidemiologists are afraid the next time such a virus mutates, it could pass from human to human; however, the current A/H5N1 virus does not transmit easily from human to human. If this form of transmission occurs, another pandemic could result. Thus, disease-control centers around the world are making avian flu a top priority. These organizations encourage poultry-related operations to develop a preemptive plan to prevent the spread of H5N1 and its potentially pandemic strains. The recommended plans center on providing protective clothing for workers and isolating flocks to prevent the spread of the virus.

The Thailand outbreak of avian flu caused massive economic losses, especially among poultry workers. Infected birds were culled and sacrificed. The public lost confidence with the poultry products, thus decreasing the consumption of chicken products. This also elicited a ban from importing countries. There were, however, factors which aggravated the spread of the virus, including bird migration, cool temperature (increases virus survival) and several festivals at that time.

In domestic animals

Several domestic species have been infected with and shown symptoms of H5N1 viral infection, including cats, dogs, ferrets, pigs,and birds.

Birds

Attempts are made in the United States to minimize the presence of HPAI in poultry thorough routine surveillance of poultry flocks in commercial poultry operations. Detection of a HPAI virus may result in immediate culling of the flock. Less pathogenic viruses are controlled by vaccination, which is done primarily in turkey flocks (ATCvet codes: for the inactivated fowl vaccine, for the inactivated turkey combination vaccine).

External links

International

United Nations System Coordinator for Avian and Human Influenza (UNSIC). Avian Influenza and the Pandemic Threat NEWLIN
World Health Organisation (WHO) WHO Avian influenza resource The United Nation's World Health Organization's Avian Flu Facts Sheet for 2006 NEWLIN
Food and Agriculture Organization of the UN (FAO) FAO Avian Influenza portal Information resources, animations, videos, photos FAO Bird Flu disease card NEWLIN
World Organisation for Animal Health (OIE) Official outbreak reports by country Official outbreak reports by week Avian influenza resource By Dr. Nati Elkin - Atlases, vaccines and information. NEWLIN

United States

PandemicFlu.Gov U.S. Government avian and pandemic flu information

CIDRAP Avian Flu Overview "Avian Influenza (Bird Flu): Agricultural and Wildlife Considerations"

US Avian Influenza Response U.S. Agency for International Development (USAID)

Avian influenza research and recommendations National Institute for Occupational Safety and Health

Influenza Research Database Database of influenza sequences and related information.

Wildlife Disease Information Node A part of the National Biological Information Infrastructure and partner of the NWHC, this agency collects and distributes news and information about wildlife diseases such as avian influenza and coordinates collaborative information sharing efforts.

Avian Influenza information AVMA - The American Veterinary Medical Association.

Species Profile- Avian Influenza (Orthomyxoviridae Influenza Type A, subtype H5N1), National Invasive Species Information Center, United States National Agricultural Library
United States National Agricultural Library
The United States National Agricultural Library is one of the world's largest agricultural research libraries, and serves as a National Library of the United States and as the library of the United States Department of Agriculture...

. Lists general information and resources for Avian Influenza.

Strategic Health Communication for Avian and Pandemic Influenza Prevention Johns Hopkins Bloomberg School of Public Health Center for Communication Programs Global Program on Avian and Pandemic Influenza.

Avian Influenza: Critical Program Issues Global Health Technical Brief on Avian Influenza.

Europe

Health-EU Portal EU response to Avian Influenza.

Avian Influenza: Prevention and Control Proceedings of the Frontis workshop on Avian Influenza: Prevention and Control, Wageningen, The Netherlands

Avian Influenza: Questions & Answers European Centre for Disease Prevention and Control - Official website

FluTrop: Avian Influenza Research in Tropical Countries French Agricultural Research Center for Developing Countries (CIRAD), Avian Influenza website

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Genetics

Subtypes

Contraction/spreading of avian influenza

Influenza pandemic

H5N1

In domestic animals

Birds

See also

External links