|
|
Common questions about avian flu |
What is avian influenza (avian flu) and how does it relate to pandemic flu? |
Avian influenza (sometimes called bird flu) refers to a large group of influenza (flu) viruses that primarily affect birds.
Avian flu viruses are common among wild birds and usually cause only mild illness, although some strains can cause serious illness with a high death rate. On rare occasions, these bird viruses can infect other species including pigs, cats, and humans. The vast majority of avian influenza viruses do not infect humans.
An influenza pandemic happens when a new flu virus emerges that has not previously circulated in humans. Influenza pandemics are caused by new influenza viruses that have adapted to spread from person to person and cause significant illness. Such viruses can arise directly from avian flu viruses or through the combination of human and avian viruses.
Avian influenza H5N1 is a strain with pandemic potential because it is widespread and has shown the ability to infect and cause severe illness in people.
For comprehensive information about pandemic influenza, see:
For more about avian influenza viruses in birds, see:
What is the current avian flu virus that everyone is so concerned about? |
The strain of avian flu virus currently of concern is called “highly-pathogenic avian influenza A H5N1”. This is the avian flu virus that caused a large outbreak in birds in Southeast Asia in 1997 and has since appeared throughout Asia and in parts of Africa, the Pacific, Europe, and the Near East affecting millions of birds. Although some countries have apparently contained their avian flu outbreaks, in many countries control measures have not been successful in stopping the spread of the virus in bird populations.
This avian flu virus is called “highly pathogenic” because it causes a high rate of death in domestic poultry. Highly pathogenic H5N1 concerns public health officials because of the possibility that it could change (through mutation or genetically combining with a human virus) in a way that would make it easy for people to spread it to each other. If this happens, a human influenza pandemic could occur.
For more information about avian influenza viruses and how a pandemic strain could develop, see the following websites:
Have any people been infected by the current strain of avian flu virus (Influenza A H5N1)? |
Yes. Compared to the very large number of infected birds, however, just a relatively small number of people worldwide have become infected with the H5N1 virus. None of these cases have been in the U.S. or the Western Hemisphere. Unfortunately, when humans do become infected, severe disease results and approximately one-half of the infected people have died.
For up-to-date information on the number of human cases and countries affected see:
How could avian flu virus from a bird infect a person? |
Avian flu viruses are shed in the feces (droppings), saliva, and nasal secretions of infected birds. People could become infected through direct contact with bird feces or body fluids including blood, or by indirect contact with surfaces contaminated by them.
The World Health Organization has investigated the cases where people have gotten the highly pathogenic H5N1 virus from birds. They have found that almost all the people infected were living in close contact with sick poultry, slaughtering poultry, or plucking feathers. There were also cases in children who played with poultry carcasses and in persons who ate pudding made with uncooked duck blood.
Nearly all of the human infections investigated have come from domestic poultry such as chickens, ducks or geese but a few infections have been related to plucking feathers from wild swans.
Where have cases of avian flu in people occurred? |
Since 1997, when the current avian flu outbreak began, over 250 people have gotten avian flu from birds. The initial human cases were in Hong Kong but cases have also occurred in Azerbaijan, Cambodia, China, Djibouti, Egypt, Indonesia, Iraq, Thailand, Turkey, and Viet Nam.
If avian flu is a common bird disease, why are scientists and government leaders so concerned about a pandemic starting? |
Influenza is common in birds and causes disease ranging from mild to severe depending on the strain of the avian flu virus and the type of bird infected. While there are dozens of strains of avian influenza, only four are known to have infected humans. These are the H7N3, H7N7, H9N2 and H5N1 strains.
The H7N3, H7N7 and H9N2 avian flu strains have caused relatively mild disease in people, but the highly pathogenic form of H5N1 is different. It has caused severe disease and death in over half the people known to have been infected with it. Scientists are concerned that if it spills over into the human population, the virus could change in such a way that it could be easily transmissible from person to person. If that happens, a human pandemic could occur. We also now know that the severe influenza pandemic in 1918-19 developed from an avian influenza virus.
Does Public Health - Seattle & King County have a plan for dealing with highly pathogenic avian flu if it occurs in wild birds or poultry in the County? |
Yes. Avian flu preparedness is included in Public Health’s comprehensive Pandemic Influenza Plan in Appendix G (PDF).
How does avian flu spread from bird to bird? |
Infected birds shed influenza virus in their saliva, nasal secretions, and feces (droppings). Susceptible birds become infected when they come into contact with excretions from infected birds or with surfaces that are contaminated with their saliva, nasal secretions or droppings. Wild bird avian flu viruses of the low pathogenic type can mix with avian viruses in domesticated birds and become highly pathogenic in domestic poultry. Poultry may become infected with avian flu virus through direct contact with infected waterfowl or other infected poultry or through contact with surfaces (such as dirt or cages) or materials (such as feces or feed) that have been contaminated with droppings that harbor the low pathogenic form of the virus.
Do migratory birds spread avian influenza viruses? |
According to the World Health Organization and other experts, the role of migratory birds in the spread of highly pathogenic avian influenza is not fully understood. Wild waterfowl are considered the natural reservoir of all influenza A viruses. They have probably carried influenza viruses, with no apparent harm, for centuries. They are known to carry avian flu viruses of the H5 and H7 subtypes, but usually in the low pathogenic form. Considerable circumstantial evidence suggests that migratory birds can introduce low pathogenic H5 and H7 viruses to poultry flocks, which then mutate to the highly pathogenic form.
Scientists believe that in the past, poultry could have been responsible for spreading the highly pathogenic virus onto wild birds, which usually died before they could spread the disease very far. Now, however, scientists believe that wild migratory birds may be playing a more significant role in spreading the H5N1 virus to new areas throughout the world.
Could migrating birds bring highly pathogenic H5N1 avian flu virus into the U.S.? |
Bird migration is one possible route of introduction of highly pathogenic H5N1 virus but it is not known how likely this could be. Other potential routes of introduction include illegal smuggling of birds or poultry products, travel by infected people, or importation of materials or equipment contaminated by the virus.
North American birds that migrate to eastern Russia, Alaska and northern Canada could come into contact with Asian birds infected with the highly pathogenic H5N1 virus. These migrating birds could potentially then bring the virus south when they return to North America.
The U.S. Fish and Wildlife Service is testing tens of thousands of birds to get an early warning that the virus has arrived. For more information, see:
If the highly pathogenic form of H5N1 avian flu virus is found in birds in our area, will people be at risk? |
If this occurs, there could be some increased risk to area residents directly exposed to wild birds or poultry, especially ill or dead birds. Eating eggs or poultry products from non-infected flocks would not be a risk. If highly pathogenic H5N1 were found in our region, public health officials would recommend precautions to minimize contact between wild birds and domestic poultry, and wild birds and people. Bird hunters and people who field dress and prepare wild birds could be most at risk.
Advice specifically for hunters is available at:
Public Health currently advises that people take precautions when handling dead birds (and dead animals of any type). This includes wearing gloves or using a shovel to pick up a dead bird, bagging dead birds in plastic bags and disposing of them in the household garbage, and washing hands thoroughly afterwards. King County residents are also asked to report dead birds to Public Health to assist in monitoring for West Nile virus and avian influenza in our area. Call 206-205-4394 or go online to report at www.metrokc.gov/health/westnile/deadbird.htm.
| |
