Avian influenza, a form of Influenza A virus is an infection caused by avian (bird) influenza (flu) viruses. These influenza viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them.
Avian Flu was first recorded in Italy more than 100 years ago in 1878. As the cause of massive poultry epidemics, this disease was then known as "Fowl Plague". This disease reared its ugly head in the United States in 1924-25, and then again in 1929. In 1955, it was determined that the virus causing Fowl Plague was one of the influenza viruses. All influenza viruses affecting domestic animals (equine, swine, avian) belong to Type A, and Type A influenza virus is the most common type producing serious epidemics in humans. Types B and C do not affect domestic animals.
Humans can be infected with influenza types A, B, and C viruses. Subtypes of influenza A that are currently circulating among people worldwide include H1N1, H1N2, and H3N2 viruses.B The reported symptoms of avian influenza in humans have ranged from typical influenza-like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections (conjunctivitis), pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications.
Outbreaks of avian influenza H5N1 have occurred among poultry in eight countries in Asia (Cambodia, China, Indonesia, Japan, Laos, South Korea, Thailand, and Vietnam) during late 2003 and early 2004. At that time, more than 100 million birds in the affected countries either died from the disease or were killed in order to try to control the outbreaks. By March 2004, the outbreak was reported to be under control. Since late June 2004, however, new outbreaks of influenza H5N1 among poultry were reported by several countries in Asia (Cambodia, China [Tibet], Indonesia, Kazakhstan, Malaysia, Mongolia, Russia [Siberia], Thailand, and Vietnam). It is believed that these outbreaks are ongoing. Influenza H5N1 infection also has been reported among poultry in Turkey Romania, and Ukraine. Outbreaks of influenza H5N1 have been reported among wild migratory birds in China, Croatia, Mongolia, and Romania.B (see map)
As of January 7, 2006, over 140 human cases of Avian influenza A (H5N1) infection have been reported in Cambodia, China, Indonesia, Thailand, Vietnam, and most recently, several cases in Turkey. A January 9, 2006 WHO Situation Report describes detection of the H5 subtype of avian influenza virus in samples from an additional 10 people in Turkey . These samples are undergoing further analysis to determine whether they contain the H5N1 strain.