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, begins to cause serious illness, and then spreads easily person-to-person worldwide.

Many scientists believe it is a matter of time until the next influenza pandemic occurs. However, the timing and severity of the next pandemic cannot be predicted. Influenza pandemics occurred three times in the past century — in 1918-19, 1957-58, and 1968-69.

Avian Influenza as a Pandemic

Scientists cannot predict whether an avian influenza (H5N1) virus will cause a pandemic. Today, H5N1 is a bird flu. There are no reported cases of sustained human-to-human passage of H5N1. However, as it mutates, it is possible the virus could become capable of passing human to human and then spread very quickly. That is why we are focusing on comprehensive public health efforts — increasing surveillance, monitoring for outbreaks, international cooperation, increasing antiviral stockpiles, and building more robust capacity for vaccine production — that will help protect us no matter what pandemic strain emerges or where.

Also see information on Avian Influenza.

Pandemic Alert Phases

The World Health Organization (WHO) developed an alert system to help inform the world about the seriousness of a pandemic. The alert system has six phases, with Phase 1 having the lowest risk of human cases and Phase 6 posing the greatest risk of pandemic. The world is presently in Phase 3 of the Pandemic Alert. This means that there is a new influenza virus subtype causing disease in humans, but is not yet spreading in an efficient (easily transmittable) and sustainable manner among humans.

(Information obtained from PandemicFlu.Gov)