What are the phases in a pandemic that the WHO has developed to prepare and plan for pandemic management?

Answer 1

The World Health Organization (WHO) has developed a system for alerts and communication of the severity or spread of an influenza epidemic, for purposes of preparedness for an influenza pandemic (see below for definition of pandemic), for the US National Preparedness Plan. They have defined six phases of outbreaks that have potential to become an influenza pandemic.

2011 ~ We are currently in the Post Pandemic Phase.

A synopsis of each phase's definition is provided below, for the full information from the WHO, see the related links section near the bottom of this answer page.

Phase 1

In nature, flu viruses circulate continuously among animals. Even though such viruses might develop into pandemic viruses, no viruses circulating among animals at the present time have been reported to cause infections in humans.

Phase 2

An animal influenza virus that is currently circulating among domesticated or wild animals is known to have caused infection in humans, and is therefore considered a potential pandemic threat.

Phase 3

There are small clusters of animal-human virus infecting people at present, these are being monitored, but it has currently not resulted in human-to-human transmission frequency sufficient to sustain community-level outbreaks, which would be required to initiate pandemic proportions.

Phase 4

There is human-to-human transmission of animal or human-animal virus able to create sustained community level outbreaks which significantly raises the level of risk of a pandemic, but does not indicate that a pandemic is a fore-gone conclusion.

Phase 5

Large areas of human-to-human transmission are occurring, and the spread has extended to at least two countries in the same region, which is a strong signal that pandemic is imminent, and containment procedures and preparedness should be being finalized.

Phase 6

The Pandemic Phase. The community level outbreaks of the virus are continually spreading among people and to at least one other country in a second region globally, and WHO declares a global pandemic is under way.

The Pandemic will progress through the post peak period of the pandemic phase and then to the post pandemic phase.

The Post Pandemic Phase

When the peak period of infection has passed and only a few outbreaks here and there remain, the WHO will declare the pandemic is over and the Post Pandemic Phase is begun. There will be continued observation and monitoring during of waves of the pandemic recurring before finally returning to the normal seasonal levels.

World Health Organization has announced that the world is now in the Post Pandemic Phase of the H1N1/09 pandemic.

World Health Organization Definition of Pandemic:

"An influenza pandemic occurs with the appearance of a new influenza virus against which none of us has any immunity. This results in several, simultaneous epidemics worldwide with high numbers of cases and deaths. With the increase in global transport and communications, as well as urbanization and overcrowded conditions, epidemics due to the new influenza virus are likely to be established quickly around the world."