TABLE 3WHO PANDEMIC PHASE DESCRIPTIONS AND MAIN ACTIONS BY PHASE

ESTIMATED PROBABILITY OF PANDEMICDESCRIPTIONMAIN ACTIONS IN AFFECTED COUNTRIESMAIN ACTIONS IN NOT-YET-AFFECTED COUNTRIES
PHASE 1UncertainNo animal influenza virus circulating among animals has been reported to cause infection in humans.Producing, implementing, exercising, and harmonizing national pandemic influenza preparedness and response plans with national emergency preparedness and response plans.
PHASE 2An animal influenza virus circulating in domesticated or wild animals is known to have caused infection in humans and is therefore considered a specific potential pandemic threat.
PHASE 3An animal or human-animal influenza reassortant virus has caused sporadic cases or small clusters of disease in people, but has not resulted in human-to-human transmission sufficient to sustain community-level outbreaks.
PHASE 4Medium to highHuman-to-human transmission of an animal or human-animal influenza reassortant virus able to sustain community-level outbreaks has been verified.Rapid containment.Readiness for pandemic response.
PHASE 5High to certainThe same identified virus has caused sustained community-level outbreaks in at least two countries in one WHO region.Pandemic response: each country to implement actions as called for in their national plans.Readiness for imminent response.
PHASE 6Pandemic in progressIn addition to the criteria defined in Phase 5, the same virus has caused sustained community-level outbreaks in at least one other country in another WHO region.
POST-PEAK PERIODLevels of pandemic influenza in most countries with adequate surveillance have dropped below peak levels.Evaluation of response; recovery; preparation for possible second wave.-
POSSIBLE NEW WAVELevel of pandemic influenza activity in most countries with adequate surveillance is rising again.Response
POST-PANDEMIC PERIODLevels of influenza have returned to the levels seen for seasonal influenza in most countries with adequate surveillance.Evaluation of response; revision of plans; recovery.

From: 4, THE WHO PANDEMIC PHASES

Cover of Pandemic Influenza Preparedness and Response
Pandemic Influenza Preparedness and Response: A WHO Guidance Document.
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