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Most people are aware of the threat of bird flu and the possibility of it creating a pandemic, a worldwide epidemic of an infectious disease breaking out and affecting a large geographic region. Although the virus affects an extensive geographic region, this virus has not yet reached pandemic proportions.

According to the World Health Organization, in order for a pandemic to occur, three conditions must be met: the emergence of a disease new to a population, the agent affects humans and causes serious illness, and the agent spreads easily and sustainably among humans.

The first of these three, 'the emergence of a disease new to a population' has occurred. Although bird flu is in no way a new disease, as it was first identified in the early 1900's, it was not infectious to humans until the late 1990's. Therefore, this particular strain has emerged 'new to a population', being the human population, which was previously unaffected by the disease.

Likewise, the second criterion has been met, 'the agent affects humans and causes serious illness'. The virus has infected 131 people and killed 68. Therefore, the severity of the disease is apparent. H5N1 causes an exaggerated response in cytokines, hormones that regulate the immune system, therefore, limiting the effectiveness of the body's ability to fight the infection. This virus is also partially resistant to other cells of the immune system, making it especially resilient.

The third condition has not been met, however. At this point, the virus does not spread easily and sustainably among humans. Currently, the H5N1 virus is only transmitted from poultry to humans, and is not able to pass through human contact. Unfortunately, the virus is mutating and may be able to do so in future months, increasing the speed and efficiency in which it spreads.

Human to human transmission has been suspected, though not confirmed. Several isolated cases in which the cause of infection was not clear have prompted questions of the virus being passed through human contact. In particular, cases of nurses becoming infected after treating patients, children being infected with no poultry contact, and parents being infected after treating children with the disease. However, until confirmation is attainable that the virus has mutated to the point human transmission is possible, the third criterion will not be satisfied and H5N1 will not be classified as a pandemic. Likewise, the fatality rate will also have to increase to change the classification of bird flu.