Avian influenza viruses are found chiefly in birds, but rare infections can occur in humans. Symptoms are generally mild, and include cough and sore throat, but more serious symptoms are possible. Because of concerns over a possible pandemic, researchers are currently studying ways of not only creating a vaccine against avian influenza, but also creating large quantities quickly.
What Is Avian Influenza?
Avian influenza -- commonly called "bird flu" or "avian flu" -- is an infection caused by influenza viruses that occur naturally in birds.
Wild birds can carry the avian influenza virus in their intestines, but usually do not get sick from it. The condition can be highly contagious among birds and can make some domesticated birds, including chickens, ducks, and turkeys, sick and even kill them. Infected birds shed the virus in their saliva, nasal secretions, and feces.
Susceptible birds become infected when they have contact with contaminated secretions, excretions, or with surfaces that are contaminated with secretions or excretions from infected birds. Domesticated birds may become infected with avian influenza virus through:
- Direct contact with infected waterfowl or other infected poultry
- Contact with infected surfaces (such as dirt or cages)
- Materials (such as water or feed) that have been contaminated with the virus.
Infection with the avian influenza virus in domestic poultry causes two main forms of the disease that are distinguished by low and high extremes of virulence. The "low pathogenic" form may go undetected, and usually causes only mild symptoms (such as ruffled feathers and a drop in egg production). However, the highly pathogenic form spreads more rapidly through flocks of poultry. This form may cause disease that affects multiple internal organs, and has a mortality rate that can reach 90 to 100 percent, often within 48 hours.
One strain of avian influenza, the H5N1 virus, is endemic in much of Asia and has recently spread into Europe. Avian H5N1 infections have recently killed poultry and other birds in a number of countries.