Biologi : Avian influenza

For the H5N1 subtype of Avian influenza see H5N1.

Avian influenza, sometimes Avian flu, and commonly bird flu refers to "influenza caused by virusess adapted to birds."

"Bird flu" is a phrase similar to "Swine flu", "Dog flu", "Horse flu", or "Human flu" in that it refers to an illness caused by any of many different strains of influenza viruses that have adapted to a specific host. All known viruses that cause influenza in birds belong to the species: Influenza A virus. All subtypes (but not all strains of all subtypes) of Influenza A virus are adapted to birds, which is why for many purposes avian flu virus is the Influenza A virus (note that the "A" does not stand for "avian").

Adaption is non-exclusive. Being adapted towards a particular species does not preclude adaptions, or partial adaptions, towards infecting different species. In this way strains of influenza viruses are adapted to multiple species, though may be preferential towards a particular host. For example, viruses responsible for influenza pandemics are adapted to both humans and birds. Recent influenza research into the genes of the Spanish Flu virus shows it to have genes adapted to both birds and humans; with more of its genes from birds than less deadly later pandemic strains.

H5N1

For more details on this topic, see H5N1 and Transmission and infection of H5N1.

The highly pathogenic Influenza A virus subtype H5N1 virus is an emerging avian influenza virus that has been causing global concern as a potential pandemic threat. It is often referred to simply as "bird flu" or "avian influenza" even though it is only one subtype of avian influenza causing virus.

H5N1 has killed millions of poultry in a growing number of countries throughout Asia, Europe and Africa. Health experts are concerned that the co-existence of human flu viruses and avian flu viruses (especially H5N1) will provide an opportunity for genetic material to be exchanged between species-specific viruses, possibly creating a new virulent influenza strain that is easily transmissible and lethal to humans.^[11][12]

Since the first H5N1 outbreak occurred in 1997, there has been an increasing number of HPAI H5N1 bird-to-human transmissions leading to clinically severe and fatal human infections. However, because there is a significant species barrier that exists between birds and humans, the virus does not easily cross over to humans, though some cases of infection are being researched to discern whether human to human transmission is occurring.^[8] More research is necessary to understand the pathogenesis and epidemiology of the H5N1 virus in humans. Exposure routes and other disease transmission characteristics such as genetic and immunological factors, that may increase the likelihood of infection, are not clearly understood. ^[13]

Although millions of birds have become infected with the virus since its discovery, 206 humans have died from the H5N1 in twelve countries according to WHO data as of November 2007. (View the most current WHO Data regarding Cumulative Number of Human Cases.)

The Avian Flu claimed at least 200 humans in romainia, Greece, turkey and Russia. Epidemioloigists are afraid that the next time such a virus mutates, it could pass from human to human. If this form of transmission occurs, another big pandemic could result. However, disease-control centers around the world are making avian flu their top priority.

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