Avian Influenza

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Avian Influenza

• By Andrew Garaniel
• University of California, Irvine

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Avian Influenza simple facts

• More commonly known as the bird flu.
• The avian influenza is caused by avian influenza
  viruses.
• The disease was first identified in Italy than
  100 years ago.

• The disease is found chiefly in birds and is
  caused by the type A strains of the influenza
  virus.

Source http//www.cdc.gov/flu/avian/gen-info/fact
s.htm http//www.who.int/csr/don/2004_01_1
5/en/
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How does it affect birds?

• Birds carry the viruses in their intestines, but
  usually do not get sick from them.
• Some birds are more resistant to the virus than
  others, with waterfowl being the most susceptible
  group of birds that can be infected with the
  disease.
• The virus can affect the birds in two ways
• Low pathogenic May go undetected and usually
  causes only mild symptoms such as ruffled
  feathers and a drop in egg production.
• High pathogenic Spreads rapidly through flocks
  of poultry and affects multiple internal organs.
  It can reach a mortality rate of 90-100 within
  48 hours.

Source http//www.cdc.gov/flu/avian/gen-info/fact
s.htm http//www.who.int/csr/don/2004_01_1
5/en/
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Spreading Avian Influenza among birds

• Infected birds shed the virus in their saliva,
  nasal secretion, and feces.
• Susceptible birds become infected when in contact
  with these contaminated secretions.
• The avian influenza is very contagious amongst
  and can spread from wild birds to domesticated
  birds like chickens and ducks.

Source http//www.cdc.gov/flu/avian/gen-info/fact
s.htm
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Subtypes of the Avian Influenza

• There are many different subtypes of type A
  influenza viruses.
• These subtypes differ because of changes in
  certain proteins on the surface of the influenza
  A virus such as Hemagglutinin and Neuraminidase
• There are 16 known Hemagglutinin subtypes and 9
  known Neuraminidase subtypes of the influenza
  viruses.

Source http//www.cdc.gov/flu/avian/gen-info/fact
s.htm
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Dangers of Influenza Subtypes

• During a 19831984 epidemic in the United States
  of America, the H5N2 virus initially caused low
  mortality, but within six months became highly
  pathogenic, with a mortality approaching 90.
• Control of the outbreak required destruction of
  more than 17 million birds at a cost of nearly
  US 65 million.
• During a 19992001 epidemic in Italy, the H7N1
  virus, initially of low pathogenicity, mutated
  within 9 months to a highly pathogenic form.
• More than 13 million birds died or were
  destroyed.

Source http//www.who.int/csr/don/2004_01_15/en/
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H5N1 Subtype of the Avian Influenza

• Human influenza viruses refer to those subtypes
  that spread from birds to humans.
• Such subtypes that can affect both birds and
  humans are H1N1, H1N2, H3N2, and H5N1.
• Out of the few subtypes that have crossed
  barriers and infected humans, H5N1 has caused the
  largest number of detected cases of severe
  disease and death in humans.
• Symptoms of a H5N1 infection range from typical
  human influenza-like symptoms such as fever,
  cough, sore throat, and muscle aches as well as
  eye infections, pneumonia, severe respiratory
  disease, and other severe life threatening
  complications.

Source http//www.pandemicflu.gov/general/
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Dangers of H5N1 Subtype virus

• Influenza viruses lack mechanisms for the
  proofreading and repair of errors that occur
  during replication.
• Influenza A viruses, including subtypes from
  different species, can swap genetic materials and
  merge.
• As populations will have no immunity to the new
  subtype, and as no existing vaccines can confer
  protection, antigenic shift has historically
  resulted in highly lethal pandemics

Source http//www.who.int/csr/don/2004_01_15/en/
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Dangers of H5N1 Subtype virus

• For this to happen, the novel subtype needs to
  have genes from human influenza viruses that make
  it readily transmissible from person to person
  for a sustainable period.
• However, it is possible that the only cases
  currently being reported are those in the most
  severely ill people, and that the full range of
  illness caused by the H5N1 virus has not yet been
  defined.

Source http//www.who.int/csr/don/2004_01_15/en/
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History of H5N1 virus on Humans

• The first documented infection of humans with an
  avian influenza virus occurred in Hong Kong in
  1997, when the H5N1 strain caused severe
  respiratory disease in 18 humans, of whom 6
  died.
• Rapid destruction of Hong Kongs poultry
  population in three days, estimated at around 1.5
  million birds, reduced opportunities for further
  direct transmission to humans, and may have
  adverted a pandemic.

Source http//www.who.int/csr/don/2004_01_15/en/
http//www.pandemicflu.gov/general/
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History of H5N1 virus on Humans

• In the current outbreaks in Asia and Europe, more
  than half of those infected with the virus have
  died.
• The infection occurred in health children and
  young adults.

Source http//www.who.int/csr/don/2004_01_15/en/
http//www.pandemicflu.gov/general/
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Outbreaks of H5 Avian Influenza in Asia (2004)
Source http//ec.europa.eu/comm/health/ph_threats
/com/Influenza/ai_jan_mar_en.htm
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Recent news of H5N1 virus on Humans

• In March 2006, the Ministry of Health of
  Azerbaijan reported to the WHO Regional Office
  for Europe a cluster of 9 suspected cases of
  human avian influenza, including 2 deaths.
• In May 2006, the Ministry of Health in Indonesia
  has confirmed an additional six cases of human
  infection with the H5N1 avian influenza virus.
  Three of these cases were fatal.

Source http//www.who.int/csr/don/2004_01_15/en/
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Possible cause to Bird Flu Pandemic

• Favorable conditions that can lead to an
  antigenic shift have been thought to involve
  humans living in close proximity to domestic
  poultry and pigs.
• Since pigs are susceptible to infection with both
  avian and mammalian viruses, they can serve as a
  mixing vessel for novel subtypes.
• Recent evidence shows that for 15 avian influenza
  virus subtypes, humans themselves can be a
  mixing vessel.

Source http//www.euro.who.int/flu/publications/2
0060511_1
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Impact of Bird Flu Pandemic

• A pandemic can last from 6 to 8 weeks.
• Severe influenza causes high levels of illness,
  death, social disruption, and economic loss.
• Impacts can range from school and business
  closings to the interruption of basic services.
• Health care facilities can be overwhelmed,
  creating a shortage of hospital staff, beds,
  ventilators and other supplies. Surge capacity at
  non-traditional sites such as schools may need to
  be created to cope with demand.
• The need for vaccine is likely to outstrip supply
  and the supply of antiviral drugs is also likely
  to be inadequate early in a pandemic.

Source http//www.pandemicflu.gov/general/impact
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Solution to H5N1 virus infection

• Viruses from human cases in Vietnam and Thailand
  show resistance to antiviral medications
  amantadine and rimantadine, which are most
  commonly used for treatment of influenza.
• This would leave two remaining antiviral
  medications, oseltamivir and zanamivir, that
  should still be effective against currently
  circulating strains of H5N1 virus.
• However, influenza viruses can become resistant
  to these drugs, so any working medications may
  not always work.

Source http//www.cdc.gov/flu/avian/outbreaks/cur
rent.htm
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Preventing Avian Influenza Pandemic

• An immediate priority is to halt further spread
  of epidemics in poultry populations.
• Most influenza experts also agree that the prompt
  culling of Hong Kongs entire poultry population
  in 1997 probably averted a pandemic.
• Workers involved in the culling of poultry flocks
  must be protected, by proper clothing and
  equipment, against infection. These workers
  should also receive antiviral drugs as a
  prophylactic measure.

Source http//www.cdc.gov/flu/avian/gen-info/fact
s.htm http//www.who.int/csr/don/2004_01_1
5/en/
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Preventing Avian Influenza Pandemic

• T here is currently a ban on the importation of
  birds and bird products from H5N1-affected
  countries.
• The regulation states that no person may import
  or attempt to import any birds, whether dead or
  alive, or any products derived from birds from
  the specified countries.
• Vaccination of persons at high risk of exposure
  to infected poultry, using existing vaccines
  effective against currently circulating human
  influenza strains, can reduce the likelihood of
  infection of humans with influenza, and reduce
  the risk that genes will be exchanged.

Source http//www.euro.who.int/flu/publications/2
0060511_1
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For further studying

• http//www.cdc.gov/flu/avian/gen-info/facts.htm
• http//www.who.int/csr/don/2004_01_15/en/
• http//www.pandemicflu.gov/general/
• http//www.cdc.gov/flu/avian/outbreaks/current.htm
  
• http//www.euro.who.int/flu/publications/20060511_
  1
• http//www.pandemicflu.gov/general/impact
• http//ec.europa.eu/comm/health/ph_threats/com/Inf
  luenza/ai_jan_mar_en.htm