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March 14, 2005

Global Flu Pandemic Appears Imminent

An article in Infection Control Today states that world health officials are closely watching continuing outbreaks of H5N1 avian (bird) influenza in Asia that are spreading to humans -- and waiting for an even more infectious variety to jump from animal to human with devastating effects.

Influenza A viruses undergo continual genetic changes, and can "swap" and merge portionsof their genetic material, the so-called "antigenic shift." This creates new viral subtypes for which human populations may have no immunity, and existing vaccines will be of no help.

According to WHO, “Conditions favorable for the emergence of antigenic shift have long been thought to involve humans living in close proximity to domestic poultry and pigs. Because pigs are susceptible to infection with both avian and mammalian viruses, including human strains, they can serve as a ‘mixing vessel’ for the scrambling of genetic material from human and avian viruses, resulting in the emergence of a novel subtype. Recent events, however, have identified a second possible mechanism. Evidence is mounting that, for at least some of the 15 avian influenza virus subtypes circulating in bird populations, humans themselves can serve as the mixing vessel.”

The article documents 10 transfers of avian influenza to humans since 1997, provides symptoms of such infections, and instructions for healthcare workers.


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