Avian Influenza

Avian influenza : infectious disease of birds

Experts already been labeled the avian flu virus, called H5N1, as one of the most dangerous driving on. The fear that pandemic is growing with the confirmation of new cases of the disease in birds. the import of birds from affected countries. U.S., meanwhile, has called for an international coalition to tackle the problem.

Avian influenza is an infectious disease of birds caused by type A strains of influenza virus. This disease was first identified in Italy more than a hundred years ago, occurs worldwide.

It is believed that all birds are susceptible to avian influenza, though some species are more resistant to infection than others. Infection causes a wide spectrum of symptoms in birds, ranging from mild illness to a highly contagious and rapidly fatal disease resulting in severe epidemics. The latter is what is known as “highly pathogenic avian influenza. This variant is characterized by sudden onset, severity of symptoms and rapid death, with a mortality that can approach 100%.

Are known 15 subtypes of influenza viruses that infect birds, thus providing an extensive reservoir of influenza viruses potentially circulating in bird populations To date, all outbreaks of the highly pathogenic form have been caused by subtypes H5 and H7 A.

Migratory waterfowl – notably wild ducks – are the natural reservoir of avian influenza viruses, and these birds are also the most resistant to infection. The domestic poultry, including chickens and turkeys are particularly susceptible to epidemics of rapidly fatal influenza.

The direct or indirect contact of domestic flocks with wild migratory waterfowl has been implicated as a frequent cause of epidemics. Live bird markets are another important link in the spread of epidemics.

A constantly mutating virus
All influenza viruses type A, including those that regularly cause seasonal epidemics in humans, are genetically labile and well adapted to elude host defenses. Influenza viruses lack mechanisms for the “proofreading” and repair of errors that occur during replication. As a result of these uncorrected errors, the genetic makeup of the viruse changes as they replicate in humans and animals, and the existing strain is replaced with a new antigenic variant. These constant changes and generally small in the antigenic composition of influenza A virus is what is called “drift” antigen.

Tags: Avian, Flu, Influenza, Tamiflu

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