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Bird Flu: Is a Pandemic Looming in Our Future?

Author(s): Deanne Erdmann, MS, Christopher Burnett, BA, and Nancy Moreno, PhD

Avian Influenzas: Change Mechanisms (part 1)

Viruses are constantly evolving, making them well adapted to escape the defenses of their hosts. Viruses, such as influenza A, are unable to “proofread” and repair errors that occur while their genetic information is being copied. As a result, these pinpoint changes (mutations) become permanent and may lead to new variants, or strains, of the virus. This process is referred to as antigenic “drift.” Agents, such as disease-causing microorganisms, that activate the immune system are called “antigens.” Thus, antigenic drift implies a slight change in the composition of a virus subtype that affects how it is recognized by the immune system. Usually, slight antigenic drifts are sufficient to allow the virus to evade immune system defenses tailored to fight another variant of the virus.