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What North American bird watchers should know about the "bird flu"
With frequent media coverage raising concerns about avian influenza, the Lab of Ornithology has compiled the following information to help you betterunderstand the virus and assess the threat.
Summary:
The "bird flu" currently found in Asia and a few locations in Europe is caused by the H5N1 strain of the avian influenza virus. Approximately 60 human deaths in Southeast Asia have been attributed to the virus since 1998. Most of these victims were in close contact with infected poultry.
As of October 2005, no cases of avian influenza (H5N1) have been detected in wild birds, domestic poultry, or people in North America.
The current risks to human health are extremely low because the virus is not easily spread between people. However, if the virus mutates into a form that can be transmitted between humans, the risk of contracting the bird flu from other people would be far greater than the risk of contracting the virus from wild or domestic birds.
Although expopsure to the bird flu is currently not a threat in North America, people can contact other illnesses from sick birds and their fecal material. Avoid handling sick birds and always wash your hands with soap and water after filling bird feeders.
There is no need to stop watching, feeding, or attracting birds to your yard because of the bird flu.
What is H5N1 and where did it come from?
The "bird flu" currently spreading through Asia and parts of Europe is of great concern due to its potential impact on populations of wild and domestic birds, and the possibility taht the virus may mutate into a form that could be easily transmitted between people.
Influenza viruses are classified by the two types of antigens, hemagglutinin (H) and neuraminidase (N), which are part of the surface of the virus. Approximately 135 different strains of influenza viruses exist, each with different combinations of the H and N proteins. Migratory waterfowl and shorebirds are the natural reservoirs for all avian influenza viruses, the majority of which do not cause any harm to these birds.
The H5N1 strain was first detected in wild terns in South Africa in 1961. The current outbreak in domestic fowl began in Hong Kong in 1997 and spread to eight Asian countries in 2003-04. The virus has continued to spread through Russia towards Europe. By October 2005, the H5N1 strain was confirmed in domestic poultry flocks in Romania, Turkey, and Greece.
How will people be affected by the bird flu?
H5N1, in its current form, is not contagious in humans. Although approximately 60 deaths have been attributed to H5N1 in Southeast Asia, these cases were associated with close contact between humans and infected domestic poultry. There have been no documented cases of H5N1 being transmitted between wild birds and humans. the risk of transmission between humans and wild birds is remote unless there is close contact with the fecal material of infected birds.
As of October 2005, there have been no cases of avian influenza caused by the H5N1 strain in birds or humans in North America. However, it is possible that the H5N1 will circulate in North America at some point in the future. The virus could be carreid to North America in any number of ways, including through trade in infected poultry or pet birds, migration of infected bird, and travel by infected people. This strain of the avian flu virus has not previously circulated in human populations, so people have not developed resistance tothe virus. A vaccine for protecting people against the H5N1 strain does not exist (October 2005), and several months would be required to develop a vaccine in the event of an outbreak in humans. However, two existing antiviral medications would likely be effective against the virus.
Will the bird flu impact bird populations?
Influenza viruses are common in wild birds, especially waterfowl and shorebirds. Although wild birds rarely become sick when infected, the H5N1 strain apparently can significantly impact wild birds as hundreds of waterfowl died during an outbreak on a reservoir in Mongolia.
It is unknown if the avian H5N1 virus can cause significant mortality in songbirds. If H5N1 does make it to North America and is spread in populatons of wild birds, long-term surveys such as Project FeederWatch will help us assess the impact of the virus.
H5N1 would certainly be a threat to domestic poultry in North America.Outbreaks of other strains of avian influenza occur from time to time in domestic poulty, leading to direct mortality and the need to cull infected flocks. In 2004, for instance, infected poultry flocks were culled following influenza outbreaks in British Columbia (H7N3 strain), Texas (H5N2 strain), and Delaware (h7N2 strain). While these outbreaks caused economic losses to the poultry farmers, no widespread effects were detected in people or wild bird populations.
FURTHER INFORMATION:
Audubon Society
World Health Organization
Centers For Disease Control
American Birding Association
National Wildlife Health Center
Cornell Laboratory of Ornithology
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