Avian Influenza

Avian InfluenzaAvian Influenza

By Andrew GaranielBy Andrew Garaniel

University of California, IrvineUniversity of California, Irvine

Avian Influenza… simple factsAvian Influenza… simple facts

• More commonly More commonly known as the bird flu.known as the bird flu.

• The avian influenza is The avian influenza is caused by avian caused by avian influenza viruses. influenza viruses.

• The disease was first The disease was first identified in Italy than identified in Italy than 100 years ago. 100 years ago.

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

Source: http://www.cdc.gov/flu/avian/gen-info/facts.htm

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

How does it affect birds?How does it affect birds? • Birds carry the viruses in their intestines, but usually do not get Birds carry the viruses in their intestines, but usually do not get

sick from them. sick from them.

• Some birds are more resistant to the virus than others, with Some birds are more resistant to the virus than others, with waterfowl being the most susceptible group of birds that can be waterfowl being the most susceptible group of birds that can be infected with the disease. infected with the disease.

• The virus can affect the birds in two ways: The virus can affect the birds in two ways: • Low pathogenic – May go undetected and usually causes only Low pathogenic – May go undetected and usually causes only

mild symptoms such as ruffled feathers and a drop in egg mild symptoms such as ruffled feathers and a drop in egg production.production.

• High pathogenic – Spreads rapidly through flocks of poultry High pathogenic – Spreads rapidly through flocks of poultry and affects multiple internal organs. It can reach a mortality and affects multiple internal organs. It can reach a mortality rate of 90-100% within 48 hours. rate of 90-100% within 48 hours.



Spreading Avian Influenza among birdsSpreading Avian Influenza among birds

• Infected birds shed the virus in their saliva, nasal secretion, and Infected birds shed the virus in their saliva, nasal secretion, and feces.feces.

• Susceptible birds become infected when in contact with these Susceptible birds become infected when in contact with these contaminated secretions. contaminated secretions.

• The avian influenza is very contagious amongst and can spread The avian influenza is very contagious amongst and can spread from wild birds to domesticated birds like chickens and ducks.from wild birds to domesticated birds like chickens and ducks.


Subtypes of the Avian InfluenzaSubtypes of the Avian Influenza

• There are many different subtypes of “type A” influenza viruses. There are many different subtypes of “type A” influenza viruses.

• These subtypes differ because of changes in certain proteins on the These subtypes differ because of changes in certain proteins on the surface of the influenza A virus such as Hemagglutinin and surface of the influenza A virus such as Hemagglutinin and Neuraminidase Neuraminidase

• There are 16 known Hemagglutinin subtypes and 9 known There are 16 known Hemagglutinin subtypes and 9 known Neuraminidase subtypes of the influenza viruses.Neuraminidase subtypes of the influenza viruses.


Dangers of Influenza SubtypesDangers of Influenza Subtypes • During a 1983–1984 epidemic in the United States of America, the During a 1983–1984 epidemic in the United States of America, the

H5N2 virus initially caused low mortality, but within six months H5N2 virus initially caused low mortality, but within six months became highly pathogenic, with a mortality approaching 90%.became highly pathogenic, with a mortality approaching 90%.

• Control of the outbreak required destruction of more than 17 million Control of the outbreak required destruction of more than 17 million birds at a cost of nearly US$ 65 million.birds at a cost of nearly US$ 65 million.

• During a 1999–2001 epidemic in Italy, the H7N1 virus, initially of low During a 1999–2001 epidemic in Italy, the H7N1 virus, initially of low pathogenicity, mutated within 9 months to a highly pathogenic form.pathogenicity, mutated within 9 months to a highly pathogenic form.

• More than 13 million birds died or were destroyed. More than 13 million birds died or were destroyed.

Source: http://www.who.int/csr/don/2004_01_15/en/

H5N1 Subtype of the Avian InfluenzaH5N1 Subtype of the Avian Influenza

• Human influenza viruses refer to those subtypes that spread from Human influenza viruses refer to those subtypes that spread from birds to humans. birds to humans.

• Such subtypes that can affect both birds and humans are H1N1, Such subtypes that can affect both birds and humans are H1N1, H1N2, H3N2, and H5N1.H1N2, H3N2, and H5N1.

• Out of the few subtypes that have crossed barriers and infected Out of the few subtypes that have crossed barriers and infected humans, H5N1 has caused the largest number of detected cases of humans, H5N1 has caused the largest number of detected cases of severe disease and death in humans.severe disease and death in humans.

• Symptoms of a H5N1 infection range from typical human influenza-Symptoms of a H5N1 infection range from typical human influenza-like symptoms such as fever, cough, sore throat, and muscle aches like symptoms such as fever, cough, sore throat, and muscle aches as well as eye infections, pneumonia, severe respiratory disease, as well as eye infections, pneumonia, severe respiratory disease, and other severe life threatening complications. and other severe life threatening complications.

Source: http://www.pandemicflu.gov/general/

Dangers of H5N1 Subtype virusDangers of H5N1 Subtype virus

• Influenza viruses lack mechanisms for the Influenza viruses lack mechanisms for the “proofreading” and repair of errors that occur during “proofreading” and repair of errors that occur during replication.replication.

• Influenza A viruses, including subtypes from different Influenza A viruses, including subtypes from different species, can swap genetic materials and merge.species, can swap genetic materials and merge.

• As populations will have no immunity to the new As populations will have no immunity to the new subtype, and as no existing vaccines can confer subtype, and as no existing vaccines can confer protection, antigenic shift has historically resulted in protection, antigenic shift has historically resulted in highly lethal pandemics highly lethal pandemics


Dangers of H5N1 Subtype virusDangers of H5N1 Subtype virus

• For this to happen, the novel subtype needs to have For this to happen, the novel subtype needs to have genes from human influenza viruses that make it genes from human influenza viruses that make it readily transmissible from person to person for a readily transmissible from person to person for a sustainable period.sustainable period.

• However, it is possible that the only cases currently However, it is possible that the only cases currently being reported are those in the most severely ill being reported are those in the most severely ill people, and that the full range of illness caused by the people, and that the full range of illness caused by the H5N1 virus has not yet been defined. H5N1 virus has not yet been defined.


History of H5N1 virus on HumansHistory of H5N1 virus on Humans

• The first documented infection of humans with The first documented infection of humans with an avian influenza virus occurred in Hong Kong an avian influenza virus occurred in Hong Kong in 1997, when the H5N1 strain caused severe in 1997, when the H5N1 strain caused severe respiratory disease in 18 humans, of whom 6 respiratory disease in 18 humans, of whom 6 died.died.

• Rapid destruction of Hong Kong’s poultry Rapid destruction of Hong Kong’s poultry population in three days, estimated at around population in three days, estimated at around 1.5 million birds, reduced opportunities for 1.5 million birds, reduced opportunities for further direct transmission to humans, and may further direct transmission to humans, and may have adverted a pandemic.have adverted a pandemic.


http://www.pandemicflu.gov/general/

History of H5N1 virus on HumansHistory of H5N1 virus on Humans

• In the current outbreaks in Asia and Europe, In the current outbreaks in Asia and Europe, more than half of those infected with the virus more than half of those infected with the virus have died.have died.

• The infection occurred in health children and The infection occurred in health children and young adults. young adults.


http://www.pandemicflu.gov/general/

Outbreaks of H5 Avian Influenza in Outbreaks of H5 Avian Influenza in Asia (2004)Asia (2004)

Source: http://ec.europa.eu/comm/health/ph_threats/com/Influenza/ai_jan_mar_en.htmhttp://ec.europa.eu/comm/health/ph_threats/com/Influenza/ai_jan_mar_en.htm

Recent news of H5N1 virus on HumansRecent news of H5N1 virus on Humans

• In March 2006, the Ministry of Health of Azerbaijan reported to the In March 2006, the Ministry of Health of Azerbaijan reported to the WHO Regional Office for Europe a cluster of 9 suspected cases of WHO Regional Office for Europe a cluster of 9 suspected cases of human avian influenza, including 2 deaths. human avian influenza, including 2 deaths.

• In May 2006, the Ministry of Health in Indonesia has confirmed an In May 2006, the Ministry of Health in Indonesia has confirmed an additional six cases of human infection with the H5N1 avian additional six cases of human infection with the H5N1 avian influenza virus. Three of these cases were fatal. influenza virus. Three of these cases were fatal.


Possible cause to Bird Flu PandemicPossible cause to Bird Flu Pandemic

• Favorable conditions that can lead to an antigenic shift have been Favorable conditions that can lead to an antigenic shift have been thought to involve humans living in close proximity to domestic thought to involve humans living in close proximity to domestic poultry and pigs.poultry and pigs.

• Since pigs are susceptible to infection with both avian and Since pigs are susceptible to infection with both avian and mammalian viruses, they can serve as a “mixing vessel” for novel mammalian viruses, they can serve as a “mixing vessel” for novel subtypes.subtypes.

• Recent evidence shows that for 15 avian influenza virus subtypes, Recent evidence shows that for 15 avian influenza virus subtypes, humans themselves can be a “mixing vessel.” humans themselves can be a “mixing vessel.”

Source: http://www.euro.who.int/flu/publications/20060511_1

Impact of Bird Flu PandemicImpact of Bird Flu Pandemic • A pandemic can last from 6 to 8 weeks. A pandemic can last from 6 to 8 weeks.

• Severe influenza causes high levels of illness, death, social Severe influenza causes high levels of illness, death, social disruption, and economic loss.disruption, and economic loss.

• Impacts can range from school and business closings to the Impacts can range from school and business closings to the interruption of basic services.interruption of basic services.

• Health care facilities can be overwhelmed, creating a shortage of Health care facilities can be overwhelmed, creating a shortage of hospital staff, beds, ventilators and other supplies. Surge capacity at hospital staff, beds, ventilators and other supplies. Surge capacity at non-traditional sites such as schools may need to be created to non-traditional sites such as schools may need to be created to cope with demand.cope with demand.

• The need for vaccine is likely to outstrip supply and the supply of 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. antiviral drugs is also likely to be inadequate early in a pandemic.

Source: http://www.pandemicflu.gov/general/#impact

Solution to H5N1 virus infectionSolution to H5N1 virus infection

• Viruses from human cases in Vietnam and Viruses from human cases in Vietnam and Thailand show resistance to antiviral medications Thailand show resistance to antiviral medications amantadine and rimantadine, which are most amantadine and rimantadine, which are most commonly used for treatment of influenza.commonly used for treatment of influenza.

• This would leave two remaining antiviral This would leave two remaining antiviral medications, oseltamivir and zanamivir, that should medications, oseltamivir and zanamivir, that should still be effective against currently circulating strains still be effective against currently circulating strains of H5N1 virus.of H5N1 virus.

• However, influenza viruses can become resistant However, influenza viruses can become resistant to these drugs, so any working medications may to these drugs, so any working medications may not always work. not always work.

Source: http://www.cdc.gov/flu/avian/outbreaks/current.htm

Preventing Avian Influenza PandemicPreventing Avian Influenza Pandemic

• An immediate priority is to halt further spread of epidemics in poultry An immediate priority is to halt further spread of epidemics in poultry populations.populations.

• Most influenza experts also agree that the prompt culling of Most influenza experts also agree that the prompt culling of Hong Kong’s entire poultry population in 1997 probably averted Hong Kong’s entire poultry population in 1997 probably averted a pandemic.a pandemic.

• Workers involved in the culling of poultry flocks must be protected, Workers involved in the culling of poultry flocks must be protected, by proper clothing and equipment, against infection. These workers by proper clothing and equipment, against infection. These workers should also receive antiviral drugs as a prophylactic measure.should also receive antiviral drugs as a prophylactic measure.



Preventing Avian Influenza PandemicPreventing Avian Influenza Pandemic

• T here is currently a ban on the importation of birds and bird T here is currently a ban on the importation of birds and bird products from H5N1-affected countries. products from H5N1-affected countries.

• The regulation states that no person may import or attempt to import The regulation states that no person may import or attempt to import any birds, whether dead or alive, or any products derived from birds any birds, whether dead or alive, or any products derived from birds from the specified countries.from the specified countries.

• Vaccination of persons at high risk of exposure to infected poultry, Vaccination of persons at high risk of exposure to infected poultry, using existing vaccines effective against currently circulating human using existing vaccines effective against currently circulating human influenza strains, can reduce the likelihood of infection of humans influenza strains, can reduce the likelihood of infection of humans with influenza, and reduce the risk that genes will be exchanged. with influenza, and reduce the risk that genes will be exchanged.

Source: http://www.euro.who.int/flu/publications/20060511_1

For further studying…For further studying… http://www.cdc.gov/flu/avian/gen-info/facts.htmhttp://www.cdc.gov/flu/avian/gen-info/facts.htm

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

http://www.pandemicflu.gov/general/http://www.pandemicflu.gov/general/

http://www.cdc.gov/flu/avian/outbreaks/current.htmhttp://www.cdc.gov/flu/avian/outbreaks/current.htm

http://www.euro.who.int/flu/publications/20060511_1http://www.euro.who.int/flu/publications/20060511_1

http://www.pandemicflu.gov/general/#impacthttp://www.pandemicflu.gov/general/#impact

http://ec.europa.eu/comm/health/ph_threats/com/Influenza/http://ec.europa.eu/comm/health/ph_threats/com/Influenza/ai_jan_mar_en.htmai_jan_mar_en.htm

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Avian Influenza