Although most people think of the flu as a single illness that returns every winter, the influenza type A virus itself — the cause of most flu outbreaks in humans — is actually in a state of almost constant change. Individuals’ immune systems, and flu vaccine manufacturers, make adjustments to account for the continuous antigenic drift in the virus, but periodically the virus also undergoes an abrupt change known as an antigenic shift. When an antigenic shift occurs, a new virus subtype suddenly emerges, catching the immune systems of its victims unaware. Sometimes, but not always, this antigenic shift results in a pandemic. The most recent influenza A pandemic to hit the U.S. occurred in 1968 and claimed 34,000 lives.

Because the influenza A virus usually mutates into a new strain every 20 to 40 years, researchers believe that the next pandemic is significantly overdue, and health care providers are beginning to take steps to prepare for it. In the blood community, AABB has taken the lead in flu pandemic preparedness efforts by establishing the AABB Interorganizational Task Force on Pandemic Influenza and the Blood Supply. The task force recently prepared documents designed to help hospitals and blood collection facilities put systems in place to alleviate the potential effects of a pandemic.
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