A pandemic is a global disease outbreak. An influenza pandemic occurs when a new influenza A virus emerges for which there is little or no immunity in the human population. Without protection, the new virus begins to cause serious illness and then spreads easily person-to-person worldwide.

It is difficult to predict when the next pandemic will happen or how serious it will be. No matter where or when it starts, everyone in the world is immediately at risk. Countries may be able to delay the arrival of the virus by taking certain measures, but they cannot avoid it.

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For more information about pandemic flu, visit the United States Government pandemic and avian flu website.

• Pandemic Flu Information