Avian Influenza A Virus subtype 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.

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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. [12]

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 Indonesia, Laos, Vietnam, Romania, China, Turkey and Russia. Epidemiologists are afraid that the next time such a virus mutates, it could pass from human to human. If this form of transmission occurs, another pandemic could result. Thus disease-control centers around the world are making avian flu their top priority.
H5N1 has been proven to be spread to domestic animals such as cats and has the potential to be spread to dogs. The disease has been known to spread from cat-to-cat however cannot be spread from cats to humans.
A vaccine developed by sanofi pasteur, Inc. is the first vaccine to be developed for H5N1: however, it has not been made accessible to the general public.

References
^ "Avian influenza strains are those well adapted to birds"EUROPEAN CENTRE FOR DISEASE PREVENTION AND CONTROL.
^ Chapter Two : Avian Influenza by Timm C. Harder and Ortrud Werner in Influenza Report 2006
^ Large-scale sequencing of human influenza reveals the dynamic nature of viral genome evolution Nature magazine presents a summary of what has been discovered in the Influenza Genome Sequencing Project.
^ Avian Influenza A (H5N1) Infection in Humans by The Writing Committee of the World Health Organization (WHO) Consultation on Human Influenza A/H5 in the September 29, 2005 New England Journal of Medicine
^ The Threat of Pandemic Influenza: Are We Ready? Workshop Summary (2005) Full text of online book by INSTITUTE OF MEDICINE OF THE NATIONAL ACADEMIES
^ [1] CDC has a phylogenetic tree showing the relationship between dozens of highly pathogenic varieties of the Z genotype of avian flu virus H5N1 and ancestral strains.
^ Evolutionary characterization of the six internal genes of H5N1 human influenza A virus
^ a b Blanchard, Ben. "China says son likely infected father with bird flu." Reuters 10 Jen 2008 10 Jen 2008 <http://www.reuters.com/article/healthNews/idUSPEK27288320080110>.
^ Chapter Two : Avian Influenza by Timm C. Harder and Ortrud Werner
^ Webster, R. G. and Walker, E. J. (2003). "The world is teetering on the edge of a pandemic that could kill a large fraction of the human population". American Scientist 91 (2): 122. doi:10.1511/2003.2.122.
^ Food Safety Research Information Office. "A Focus on Avian Influenza". Created May 2006, Updated November 2007.
^ World Health Organization. (2006). Avian influenza (" bird flu") – The Disease in Humans. Retrieved April 6, 2006.