Avian Influenza

Avian influenza is a contagious viral infection that can affect all species of birds (chickens, turkeys, guinea fowl, pet birds and wild birds). In intensive poultry rearing systems, young fattening turkeys and laying hens are usually the most affected species.

Wild birds may carry influenza viruses without becoming ill due to natural resistance. Wild waterfowl present a natural reservoir for these viruses and can be responsible for the primary introduction of infection into domestic poultry. Signs of the disease range from a mild infection with no symptoms to a severe epidemic that kills up to 100 percent of infected birds.

What's the status of avian influenza in B.C.?

The Canadian Food Inspection Agency (CFIA) depopulated all premises (42 commercial and 11 backyard premises) on which highly pathogenic avian influenza was found and those in the surrounding three kilometre areas.

The response effort is now entering the recovery phase, shifting from depopulation to decontamination and surveillance. Led by industry, the decontamination program, which involves rigorously cleaning and disinfecting barns, vehicles and tools, is intended to eliminate any traces of the virus that may remain on infected premises. Active surveillance of poultry is increasing throughout the control area to detect any cases of infection that may remain. If present, infected birds will be depopulated immediately. As an additional precaution, movement control on birds and bird products will remain in effect, while some movement restrictions have been eased.

For additional information, please visit the CFIA web site at www.inspection.gc.ca.

What strain of avian influenza was in B.C.?

Both low and high pathogenic strains of H7N3 were found in B.C. This is not the same virus that currently exists in Asia. It is also different from the strains of avian influenza found in the United States.

What's the status of H5N1 avian influenza in Asia?

Eight countries in Asia experienced outbreaks of H5N1 avian influenza in winter of 2003-2004. This led to control measures which included slaughtering of more than 100 million poultry. There were 34 human cases of avian influenza infection and 23 deaths. Given the extensive nature of the outbreak and demonstrated ability of this virus to result in serious human illness, Health Canada and its partners continue to remain vigilant for the potential re-emergence in poultry and transmission to humans. Surveillance of avian influenza activity continues in Canada and throughout the world.

Are there recurrences of H5N1 in Asia?

Vietnam, Thailand and China are reporting new cases of avian influenza in poultry. Vietnam is also reporting human cases of H5N1.

Is avian influenza transmissible to humans?

In rare instances people can contract avian flu. To date, the H5N1, H7N7 and H9N2 subtypes of the avian influenza virus have been known to cause illness in people, with H5N1 associated with the most serious illness in humans.

H7N2 virus was detected in poultry in Delaware and did not cause illness in humans. An outbreak of H7N7 in the Netherlands in 2003 resulted in one death and over 80 cases of mild disease in people. The vast majority of these cases exhibited conjunctivitis, and some of them displayed mild influenza-like illness.

In B.C., two people were infected with avian influenza. Both cases of infection followed close contact with infected poultry and contaminated materials and resulted in mild symptoms. Both people have fully recovered.

What's the difference between high and low pathogenicity?

The virus is considered low or highly pathogenic based on the severity of the illness in the bird population. Highly pathogenic avian influenza escalates rapidly from the onset of symptoms to severe illness and death in the bird population. Deaths in the bird population can approach 100% when the virus is highly pathogenic. Low pathogenic viruses cause less serious illness and the affected birds often recover.

What does this mean for people?

Low and high pathogenicity refers to how the virus behaves in birds. Every precaution has and continues to be taken to protect human health regardless of the virus' pathogenicity.

What do the H and the N mean?

These letters refer to surface proteins on the influenza virus that determine its subtype.

Could H7 have become the next pandemic?

The chances of this were very low but we put public health measures in place to protect Canadians because avian influenza outbreaks in birds increase opportunities for human exposure to the virus. If a person sick with a human influenza virus was also infected with the avian influenza virus, the viruses could re-assort or "mix." This means that the avian influenza virus acquires human influenza genes, potentially creating a new subtype of the influenza A virus that people would have no immunity against.

Can mosquitoes transmit avian influenza from birds to people like West Nile?

There is no evidence that the influenza virus can be transmitted by mosquitoes.

Is the general public at risk from human cases of H7?

The risk would be low. The people most risk in this type of situation would be are those who are in close contact with infected poultry. All known cases of infection associated with avian influenza in B.C. had close contact with infected poultry. Close contact means either handling or being in a confined airspace with the infected birds.

Should individuals get a flu shot to guard against avian influenza?

The current season flu shot does not protect against avian influenza. Immunization with the current season flu vaccine would be important though for those in close contact with infected poultry because it could reduce the likelihood that a worker would be infected with the human and avian forms of influenza at the same time. If a person were infected with both viruses at the same time, there is a possibility that the two viruses will "mix" and create a new virus against which people have no immunity.

Above content taken from the official Health Canada web site.

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