Frequently Asked Questions: Avian Influenza
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What is avian influenza?
Avian influenza is a contagious viral infection that can affect all species of birds but can, less commonly, infect mammals. While all bird species are thought to be susceptible to infection, domestic poultry flocks are especially vulnerable to infections that can rapidly turn into epidemics. 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. Further evolution of these viruses amongst poultry may result in strains that are capable of causing a wide range of clinical illness, from no symptoms to a severe epidemic that kills up to 100 percent of infected birds.
Is avian influenza transmissible to humans?
People have contracted avian flu and limited, inefficient human-to-human transmission is suspected in some cases. To date, the avian influenza viruses that have caused illness in people include the H5N1, H7N7, H7N3 and H9N2 subtypes, with H5N1 associated with the most serious illness in humans.
Since January 2004, widespread outbreaks of H5N1 in birds in Asian countries have been associated with human cases and deaths in Asia.
In B.C., two people were infected with avian influenza during a H7N3 outbreak in poultry in 2004. Both cases of infection followed close contact with infected poultry and contaminated materials and resulted in mild symptoms. Both people recovered fully.
In February 2003, the H5N1 strain jumped from birds to infect two members (father and son) of a family from Hong Kong who had travelled to southern China. The father died but the son recovered. A third member of the family, the boy’s sister, died of a severe respiratory illness in China.
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.
The first documented human infection with H5N1 occurred in Hong Kong in 1997. In that first outbreak, 18 people were hospitalised and 6 of them died.
Why are so many people in places like Vietnam and Thailand dying?
An increase in human cases of avian influenza in Vietnam and Thailand coincides with new outbreaks of the virus in birds. Avian influenza will remain a threat as long as the virus is circulating in the country. Avian influenza viruses become more active in cooler temperatures so it is likely that we’ll continue to see more poultry outbreaks as well as human cases.
To date, most human cases have been linked to direct contact with infected poultry. Often, this contact includes high risk exposure during the slaughter, de-feathering and preparation of poultry for cooking.
Poultry marketing, transportation and consumption also increases in Vietnam with the approach of the Lunar New Year in early February. These activities create conditions favourable for poultry outbreaks.
Is there a vaccine for H5N1?
A vaccine is not currently available. At this point though, a genetically modified seed strain for H5N1 vaccine development is available and vaccine manufacturers in several countries, including Canada have acquired this seed strain. Manufacturers are working now to optimize the conditions under which the modified H5N1 virus grows in eggs. This will allow them to develop a virus seed bank for future vaccine production.
The virus has been modified using a technique called reverse genetics so that it can grow in chicken eggs, the main source of influenza vaccine production. The genetic modification also makes the virus less virulent.
How many people have died in these countries?
The WHO provides the most recent information on the cumulative number of cases and deaths since January 28, 2004. Please visit the WHO web site.
Is avian flu activity in these regions increasing?
According to the World Health Organization and the World Organization for Animal Health, outbreaks in birds in Vietnam appear to be increasing since December 2004, especially in the southern areas. The number of human cases is currently not that different from what we’ve seen in 2004. Increasing outbreaks among birds in the affected countries increases the chances for human exposure to the virus.
What is Canada doing to help these countries and to prevent the international spread of the virus?
The Public Health Agency of Canada has provided communications and public health support to the region. The Agency continues to work with the WHO, other international organizations and other countries to improve the prevention and control of avian influenza and pandemic influenza preparedness.
Is H5N1 going to evolve into a strain of pandemic influenza?
We don’t know for sure whether or not H5N1 will evolve into a pandemic strain but it has shown the ability to mutate so it is a concern. Influenza viruses are constantly changing over time and it is possible that changes in the virus currently affecting Vietnam and Thailand can result in a virus that is more efficiently transmissible to and among humans. While there have recently been changes in the virus, there is currently no indication that the virus has changed to a form that could result in a pandemic. This possibility is being closely monitored.
How will we know if H5N1 is becoming a pandemic strain?
If H5N1, or any other strain of avian influenza, were to evolve into a pandemic strain of influenza, we expect, based on the scientific research that’s been done, that we would see efficient and sustained human-to-human transmission of the virus. This means we would see a large and growing number of new and unrelated cases increasing daily which, to date, has not been the case.
What is the Public Health Agency of Canada doing to protect Canadians from the next pandemic?
The Public Health Agency of Canada, together with other federal government departments and provincial and territorial governments, has taken and continues to take action in a number of areas to protect Canadians. Activities include:
- Maintaining the Canadian Pandemic Influenza Plan.The plan maps out how Canada will prepare for and respond to pandemic influenza. The Agency continues to work on the plan based on new information that comes available. The plan also provides a model for responding to other infectious disease outbreaks.
- Establishing a contract for pandemic vaccine production. Canada is the first country worldwide to plan for a secure vaccine supply through the contracting of a domestic supplier.
- Creating a national antiviral stockpile for use against an influenza pandemic. The national antiviral stockpile will be used to treat identified priority groups agreed upon by a national expert committee.
- Managing the National Emergency Stockpile System (NESS). The NESS contains everything that you would expect to find in a hospital, from beds and blankets and a supply of pharmaceuticals. This includes a stockpile of antiviral medication.
- Providing international leadership on pandemic preparedness. Canada is collaborating with the WHO, other international organizations and other countries to improve global pandemic preparedness. Canada is co-leading with the United Kingdom discussions related to the supply and use of antivirals within the Global Health Security Action Group with the G7 plus Mexico.
- Managing a real-time alert system for serious respiratory illnesses (SRIs), including SARS and avian influenza, to ensure timely dissemination of information to the provinces and territories.
- Putting in place a hospital-based surveillance system to detect cases and clusters of severe or emerging respiratory infections and to effectively prevent and contain their spread in acute care facilities.
- Monitoring the global situation and verifies information received from the Global Public Health Information Network (GPHIN) alert system. GPHIN tracks thousands of global media stories on public health issues and allows the Public Health Agency to quickly identify and monitor cases of severe respiratory infections around the world.
- Ongoing support and maintenance of Quarantine Services at the Toronto, Vancouver, Montreal (Pierre Elliot Trudeau), Calgary, Edmonton, Halifax and Ottawa international airports. Quarantine officers provide health assessments for international traveller who have signs of illness.
What do the H and the N mean?
These letters refer to surface proteins, hemagglutinin (H) and neuraminidase (N), on the influenza virus that determine its subtype.
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 causes a severe disease that 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.
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 in 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.
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.
Source: Public Health Agency of Canada
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