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Where we are: Since 2004, some 270 humans have been infected with bird flu in 10 countries, with about 167 fatalities, mostly in Asia, according to the World Health Organization.

Background: With the flu spreading around the world, the virus has turned up in birds in Asia, Europe and Africa. So far, bird flu has mostly been passed from birds either to other birds or, in isolated cases, to humans. In June 2006, WHO reported the first case of human transference of the disease, when an Indonesian man died after catching the flu from his 10-year-old son. If the flu mutates into a strain that can pass more readily from human to human, people will have no immunity and the flu will probably pass rapidly from person to person, creating a pandemic. Flu vaccines can only be made to protect against a particular virus, and, since the virus had yet to be passed from human to human, no vaccine has been developed.

In Asia, many people live with ducks and chickens in their homes and in their yards. Health and veterinary officials worldwide announced that a key way to stop the spread of the disease is to improve farming practices, segregating poultry from humans, and culling birds that have been infected with the deadly virus.

What's next? When asked for predictions as to the seriousness of the pandemic, should one occur, experts have based their projections on a similar pandemic that occurred in 1918-1919. Up to a billion people fell ill, and nearly 100 million died worldwide. Translating to today's figures, they project that some 30-60 percent of the world's population could be infected by the virus, and over 300 million people worldwide could die.

An ounce of prevention.... Since the avian flu virus is destroyed by heat, be sure to eat only well-cooked poultry and eggs. Make sure that utensils and kitchen surfaces where eggs and raw poultry are handled are kept clean. Separate raw poultry from cooked foods. In the meantime, good hygiene remains the best prevention: keep hands well-washed, and avoid contact with people who have been infected with the virus.

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Bird Flu

Hundreds of thousands of birds in Asia died due to a virus that has been dubbed the "bird flu." The highly contagious illness is responsible for wiping out large numbers of poultry in Japan, South Korea, Taiwan and Vietnam. The particular strain of influenza which has been reported as causing the deaths is called H5N1. Humans can contract the disease through close contact with infected birds, or with the feces of infected birds. It is not known to spread through human-to-human contact. There has been no indication that humans would get the disease through eating eggs or meat of sick birds.

The only known way to eradicate the disease is by culling infected flocks. Thus far millions of chickens, ducks and other kinds of poultry have been culled in an effort to eliminate the virus. There have been several deaths due to the flu and the World Health Organization has expressed concern that the virus could latch on to a human influenza virus, potentially causing a serious epidemic. The bird flu's symptoms in humans include fever and coughing and eventual pneumonia.

Last updated: November 02, 2004.

 
 

viral respiratory disease, mainly of birds including poultry and waterbirds but also transmissible to humans. Symptoms in humans include fever, sore throat, cough, headache, and muscle aches. Severe infections can result in life-threatening complications such as pneumonia and acute respiratory illness. The first known human cases occurred in Hong Kong in 1997, resulting in six deaths. Deadly outbreaks among poultry in several countries in eastern and central Asia between 2003 and mid-2005 were accompanied by more than 100 human cases, about half of them fatal. The causative agents are virus subtypes related to the human influenza type A viruses, the most virulent and contagious being the H5N1 subtype. A specific protective vaccine for this virus remains to be developed. Studies suggest that some antiviral drugs that work against human influenza may be effective in treating bird flu in humans.

For more information on bird flu, visit Britannica.com.

 
Wikipedia: avian influenza

Avian flu (also "bird flu", "avian influenza", "bird influenza"), means "flu from viruses adapted to birds", but is sometimes mistakenly used to refer to both other flu subsets (such as H5N1 flu) or the viruses that cause them (such as H5N1).[1][2][3][4][5][6][7]

"Bird flu" is a phrase similar to "Swine flu", "Dog flu", "Horse flu", or "Human flu" in that it refers to an illness caused by any of many different strains of flu viruses such that the strain in question has adapted to the host. "Avian flu" differs in being named after an entire vertebrate class with 8,800–10,200 species. All known avian flu viruses belong to the species of virus called Influenza A virus. 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 sometimes partial or multiple so a flu virus strain can be partially adapted to a species or adapted to more than one species. Flu pandemic viruses are human adapted and also bird adapted. Being adapted to one species does not mean another species can not catch it; nor does it mean it can not adapt to another species.

Genetics

Genetic factors in distinguishing between "human flu viruses" and "avian flu viruses" include:

PB2: (RNA polymerase): Amino acid (or residue) position 627 in the PB2 protein encoded by the PB2 RNA gene. Until H5N1, all known avian influenza viruses had a Glu at position 627, while all human influenza viruses had a lysine.
HA: (hemagglutinin): Avian influenza HA bind alpha 2-3 sialic acid receptors while human influenza HA bind alpha 2-6 sialic acid receptors. Swine influenza viruses have the ability to bind both types of sialic acid receptors.

The HA changes have not yet occurred in any sequenced H5N1 virus - even ones from humans that died from it and the PB2 changes don't stop it from being a flu virus adapted to birds (the definition of "avian flu virus").

Influenza pandemic

For more details on this topic, see Influenza pandemic.

Pandemic flu viruses have some avian flu virus genes and usually some human flu virus genes. Both the H2N2 and H3N2 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 virus strain may have been transmitted directly from birds to humans.[8]

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 doesn't 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 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 in days over 90% of an entire flock and spread to other flocks and kill 90% of them and can only be stopped by killing every domestic bird in the area. Until H5N1 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 has evolved into a flu virus strain that infects more species than any previously known flu virus strain, is deadlier than any previously known flu virus strain, and continues to evolve becoming both more widespread and more deadly causing 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. He called for adequate resources to fight what he sees as a major world threat to possibly billions of lives.[9] Since the article was written, the world community has spent billions of dollars fighting this threat with limited success.

Cumulate Human Cases of and Deaths from H5N1
As of April 11 2007
Image:H5n1 spread (with regression).png

Notes:

H5N1

Main articles: H5N1 and H5N1 flu

As of 2007, "avian flu" is being commonly used to refer to infection from a particular subtype of Influenza A virus, H5N1, which can cause severe illness in humans who are infected. Currently, this strain is transmitted by contact with infected birds, and has been transmitted from one person to another only in a few cases. H5N1 flu is therefore not pandemic now and is not currently capable of causing a pandemic. Only if H5N1 mutates into a form that can be readily transmitted from one person to another could it cause a pandemic.

On August 22, 2007, an Indonesian woman, 28, chicken trader was the 2nd person to die of bird flu on Bali, raising the death toll in the nation due to the disease to 84 (after 4 days of hospitalization). Tests in 2 local laboratories was positive for the H5N1 strain of the disease. 194 people — the majority of them in Indonesia died since 2003, according to the World Health Organization. [10]

Illustrative examples of correct usage

H5N1
Colorized_transmission_electron_micrograph_of_Avian_influenza_A_H5N1_viruses.jpg
WHO pandemic phases
  1. Low risk
  2. New virus
  3. Self limiting
  4. Person to person
  5. Epidemic exists
  6. Pandemic exists
Swans can carry highly pathogenic avian H5N1 and other avian flu viruses
Enlarge
Swans can carry highly pathogenic avian H5N1 and other avian flu viruses

In technical contexts, correct usage of terms is necessary because precise distinctions are the essence of the communication.

  • "Avian influenza strains are those well adapted to birds"[1]
  • "An outbreak of influenza A (H5N1), also known as 'avian flu' or 'bird flu,' has been reported in several countries throughout Asia."[11]
  • "Avian influenza virus usually refers to influenza A viruses found chiefly in birds, but infections can occur in humans."[12]
  • "Of the few avian influenza viruses that have crossed the species barrier to infect humans, H5N1 has caused the largest number of cases of severe disease and death in humans. Unlike normal seasonal influenza, where infection causes only mild respiratory symptoms in most people, the disease caused by H5N1 follows an unusually aggressive clinical course, with rapid deterioration and high fatality." Seasonal influenza is human flu.[13]
  • "avian influenza HA bind alpha 2-3 sialic acid receptors while human influenza HA bind alpha 2-6 sialic acid receptors. Swine influenza viruses have the ability to bind both types of sialic acid receptors."[14]
  • Sometimes a virus contains both avian adapted genes and human adapted genes. Both the H2N2 and H3N2 pandemic strains contained avian flu virus RNA segments. "While the pandemic human influenza viruses of 1957 (H2N2) and 1968 (H3N2) clearly arose through reassortment between human and avian viruses, the influenza virus causing the 'Spanish flu' in 1918 appears to be entirely derived from an avian source (Belshe 2005)."[2]

Illustrative examples of imprecise usage

In nontechnical contexts, imprecise usage of terms is typical when discussing complex things.

  • "A 1,000 square mile quarantine zone to combat an outbreak of bird flu was lifted in Scotland today - despite the spread of a similar disease south of the border." Here "bird flu" is used to mean "Asian lineage HPAI A(H5N1) flu" (which is a bird flu) and contrasted with flu from an avian adapted strain of H7N3 (which is also a bird flu).[15]

Unanswered questions

Experts say many key questions hover around the disease:[16][17][18]

  • No one knows how many could die.
  • No one knows how far it has spread. In Africa "surveillance is so poor that deaths of chickens or humans could easily go undiagnosed for weeks."
  • No one knows much about future pandemic mutations, except they are increasingly likely due to millions more birds in many more countries leading "to an exponential increase of the load of virus in the world [...] Each infected bird and person is actually awash in minutely different strains, and it takes lengthy genetic testing to sequence each one - so if a pandemic strain were to appear it might be quite difficult for us to pick up that change when it happens."
  • No one knows why "the disease, after years of smoldering in poultry, suddenly start hitchhiking in migratory birds."
  • No one knows why "the northern China strain - the one now spreading westward - cause[s] so many false negatives in diagnostic tests".
  • No one knows why so many people fell sick so quickly in Turkey.
  • No one knows the significance of H5N1 spread by mammals such as cats.
  • No one knows enough about what virus strains are in which bird species to make useful predictions.
  • No one knows enough about bird migration patterns to make useful predictions. Bird species' migration strategies can vary according to age, sex, weather and season, among other things.
  • No one knows how lethal the next influenza pandemic will be.
  • No one knows when it will occur.
  • No one knows if any of the prepandemic vaccines now being tested will have been of any use when the pandemic happens.
  • No one knows if any of the nonvaccine drugs will be of any use against the pandemic virus when it comes.
  • No one knows if H5N1 will ever go away.

See also

Timeline data on avian flu
Subtypes of the causative agent species of avian flu include
Information concerning research about it can be found at

Sources and notes

  1. ^ a b "Avian influenza strains are those well adapted to birds"EUROPEAN CENTRE FOR DISEASE PREVENTION AND CONTROL.
  2. ^ a b Chapter Two : Avian Influenza by Timm C. Harder and Ortrud Werner from excellent free on-line Book called Influenza Report 2006 which is a medical textbook that provides a comprehensive overview of epidemic and pandemic influenza.
  3. ^ Large-scale sequencing of human influenza reveals the dynamic nature of viral genome evolution Nature magazine presents a summary of what has been discovered in the Influenza Genome Sequencing Project.
  4. ^ Full HTML text of Avian Influenza A (H5N1) Infection in Humans by The Writing Committee of the World Health Organization (WHO) Consultation on Human Influenza A/H5 in the September 29, 2005 New England Journal of Medicine
  5. ^ The Threat of Pandemic Influenza: Are We Ready? Workshop Summary (2005) Full text of online book by INSTITUTE OF MEDICINE OF THE NATIONAL ACADEMIES
  6. ^ Here is the tree showing evolution by antigenic drift since 2002 that created dozens of highly pathogenic varieties of the Z genotype of avian flu virus H5N1, some of which are increasingly adapted to mammals.
  7. ^ Evolutionary characterization of the six internal genes of H5N1 human influenza A virus
  8. ^ Chapter Two : Avian Influenza by Timm C. Harder and Ortrud Werner from excellent free on-line Book called Influenza Report 2006 which is a medical textbook that provides a comprehensive overview of epidemic and pandemic influenza.
  9. ^ Webster, R. G. and Walker, E. J. (2003). "The world is teetering on the edge of a pandemic that could kill a large fraction of the human population". American Scientist 91 (2): 122. doi:10.1511/2003.2.122. 
  10. ^ ITH, Bird flu kills Balinese woman, raises death toll to 84
  11. ^ OSHA
  12. ^ CDC Avian Influenza (Bird Flu)
  13. ^ WHO Avian influenza frequently asked questions
  14. ^ Greninger Paper (PDF)
  15. ^ News Avian flu quarantine zone lifted published May 1 2006.
  16. ^ ISP News article Four Years On Questions Hover on Bird Flu published October 16, 2007
  17. ^ NYT article picked up by IHT
  18. ^ International Institute for Sustainable Development (IISD) SCIENTIFIC SEMINAR ON AVIAN INFLUENZA, THE ENVIRONMENT AND MIGRATORY BIRDS ON 10-11 APRIL 2006 published 14 April 2006.

Further reading

Official - international
Official - United States
  • PandemicFlu.Gov U.S. Government's avian flu information site
  • USAID U.S. Agency for International Development - Avian Influenza Response
  • CDC Centers for Disease Control - responsible agency for avian influenza in humans in US - Facts About Avian Influenza (Bird Flu) and Avian Influenza A (H5N1) Virus
  • USGS - NWHC National Wildlife Health Center - responsible agency for avian influenza in animals in US
  • HHS U.S. Department of Health & Human Services - Pandemic Influenza Plan
Official - United Kingdom
Technical
General information
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