WHO PHASES OF PANDEMIC ALERT

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Ashwin Udyavar

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Aug 29, 2009, 12:08:02 PM8/29/09

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WHO PHASES OF PANDEMIC ALERT(Source: WHO)
Phase 1 No animal influenza virus circulatingamong animals has been
reported to cause infections in humans.

Phase 2 An animal influenza virus circulatingamong domesticated or
wild animalsis known to have caused infection inhumans, and is
therefore considereda specific potential pandemic threat.

Phase 3 An animal or human-animal influenzareassortant virus has
caused sporadiccases or small clusters of disease inpeople, but has
not resulted in human-to-human transmission sufficient tosustain
community-level outbreaks.

Phase 4 Human-to-human transmission(H2H)ofan animalor
human-animalinfluenza reassortant virus able tosustain
“community-level outbreakshas been verified.

Phase 5 The same identified virus has causedsustained community level
outbreaksin two or more countries in one WHO region

Phase 6 The pandemic phase,ischaracterized by community leveloutbreaks
in at least one other country in a different WHO region in addition
tothe criteria defined in Phase 5.Post PeakPeriodLevels of pandemic
influenza in mostcountries with adequate surveillancehave dropped
below peak levelsPossiblenew waveLevel of pandemic influenza activity
inmostcountrieswithadequatesurveillance rising
againPostPandemicPeriodLevels of Influenza activity havereturned to
levels seen for seasonalinfluenza in most countries withadequate
surveillance