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Avian Influenza

Avian Influenza. By Andrew Garaniel University of California, Irvine. 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.

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Avian Influenza

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  1. Avian Influenza By Andrew Garaniel University of California, Irvine

  2. 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. Avian Influenza… simple facts Source: http://www.cdc.gov/flu/avian/gen-info/facts.htm http://www.who.int/csr/don/2004_01_15/en/

  3. 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/facts.htm http://www.who.int/csr/don/2004_01_15/en/

  4. 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/facts.htm

  5. 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/facts.htm

  6. Dangers of Influenza Subtypes • During a 1983–1984 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 1999–2001 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/

  7. 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/

  8. 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/

  9. 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/

  10. 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 Kong’s 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/

  11. 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/

  12. Outbreaks of H5 Avian Influenza in Asia (2004) Source: http://ec.europa.eu/comm/health/ph_threats/com/Influenza/ai_jan_mar_en.htm

  13. 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/

  14. 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/20060511_1

  15. 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

  16. 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/current.htm

  17. 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 Kong’s 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/facts.htm http://www.who.int/csr/don/2004_01_15/en/

  18. 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/20060511_1

  19. 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/Influenza/ai_jan_mar_en.htm

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