Avian influenza.

              What is avian influenza?
Avian influenza, or “bird flu,” is an infection caused by influenza A viruses, which normally infect only birds. These influenza A viruses are found in wild birds worldwide and are quite contagious among birds. In many wild species of birds, especially in birds that swim or live near water including ducks, geese and gulls, infection with avian influenza generally does not cause illness, but may lead to serious disease in domesticated birds such as chickens, ducks, and turkeys .
What types of avian influenza viruses are there and which cause serious disease in birds?
Influenza A viruses are classified into subtypes based on certain proteins present on the outer layer of the virus. These proteins are hemagglutinin (H) and neuraminidase (N). There are 16 different H subtypes and 9 different N subtypes. Any combination of these two protein types is possible to form a virus subtype, for example H9N3, H7N7, or H5N1. The ability of avian influenza viruses to cause serious disease (pathogenicity) tends to vary with the makeup or subtype of the virus. Subtypes that are classified as “low path” cause mild symptoms of illness in birds such as ruffled feathers and a drop in egg production. “High path” virus subtypes cause more severe disease, spread rapidly through a flock, and kill a significant number of birds. Presently, only H5 and H7 subtypes cause severe disease outbreaks in birds.
How common is avian influenza?
Avian influenza outbreaks among poultry occur worldwide from time to time. Since 1997, more than 16 outbreaks of H5 and H7 influenza have occurred among poultry in the United States.
How is avian influenza controlled?
When avian influenza outbreaks occur in poultry such as chickens or turkeys, animal health officials use quarantine, surveillance, and re-duction in the number of birds (or culling) in the affected flock to control and stop the spread of disease.
How does avian influenza spread?
Infected birds shed the influenza virus in their respiratory discharges and droppings. Birds may be infected when they come into contact with contaminated excretions or surfaces. The occurrence of human infections is rare since avian influenza viruses are adapted to birds and usually do not infect humans. Most cases of avian influenza in humans have resulted from contact with infected poultry or contaminated surfaces such as feed, water, equipment, cages, or clothing. Exposure to humans is considered most likely during slaughter, removing feathers, butchering, or preparation of infected poultry for cooking.
What are the symptoms of avian influenza in humans?
The symptoms of avian influenza in humans depend on the characteristics of the infecting virus. In most cases, the symptoms will be absent or mild consisting of fever, headache and eye inflammation (conjunctivitis). Rarely, symptoms may be more severe including high fever, cough, sore throat, pneumonia, acute respiratory distress, and other severe and life-threatening complications.
How commonly do avian influenza viruses affect humans?
Although avian influenza A viruses usually do not infect humans, several instances of human infections have been reported since 1997. Most cases of avian influenza infection in humans are thought to have resulted from direct contact with infected poultry or contaminated surfaces such as feed, water, equipment, cages or clothing. These human cases of influenza have been in poultry workers and farmers who raise chickens, turkeys or ducks, as well as in people who work in live bird markets.
What is the H5N1 avian influenza virus that has been found in Asia and Europe?
Influenza A (H5N1) virus – also called “H5N1 virus” – is an influenza A virus subtype that occurs mainly in birds. Its first significant recognition was in 1997 in Hong Kong where it was determined to be the cause of poultry disease outbreaks and 18 associated human cases of severe respiratory illness. Over one million birds were destroyed to control the disease spread.
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Avian Influenza
Public Health
Fact Sheet
Public Health
Fact Sheet
The Asian H5N1 “bird flu” is not present anywhere in North America. There have been no records of positive tests in wild or do-mestic birds, or cases of human illness in the U.S.