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Emergency Management


Pandemic Stages

According to the Centers for Disease Control and Prevention (CDC), pandemic influenza occurs when a new influenza A virus emerges for which there is little or no immunity in the human population. The virus then begins to cause serious illness and then spreads easily person-to-person worldwide. Characteristics of a pandemic influenza include rapid worldwide spread, overwhelming of healthcare systems, inadequate medical supplies, and economic and social disruption.
National and federal organizations have classified stages of pandemic influenza to better formulate guidance based on the impact of the virus. This section of the guide details these classifications.

World Health Organization

The World Health Organization (WHO) has developed a method for classifying the rate of worldwide transmission of an influenza virus. This method, known as the WHO pandemic phases1, identifies six phases of an influenza pandemic across three pandemic periods.

Inter-Pandemic Period

Pandemic Alert Period

Pandemic Period

United States Government

The Department of Health and Human Services and CDC work closely to plan for, respond to, and recover from emerging disease outbreaks, including pandemic influenza. While these efforts are constantly evolving, the national strategy is based on three (3) pillars2: