WHO AND H1N1

WHO has two main indicator , when it dealt with influenza virus outbreak.

The first one is Pandemic Alert Level,which defines the stages of a pandemic, outlines WHO's role and makes recommendations for national measures before and during a pandemic.The chart is given below

WHO Pandemic Influenza Phases (2009)
Phase	Description
Phase 1	No animal influenza virus circulating among animals have been reported to cause infection in humans.
Phase 2	An 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 3	An 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 4	Human to human transmission of an animal or human-animal influenza reassortant virus able to sustain community-level outbreaks has been verified.
Phase 5	Human-to-human spread of the virus in two or more countries in one WHO region.
Phase 6	In addition to the criteria defined in Phase 5, the same virus spreads from human-to-human in at least one other country in another WHO region.
Post peak period	Levels of pandemic influenza in most countries with adequate surveillance have dropped below peak levels.
Post pandemic period	Levels of influenza activity have returned to the levels seen for seasonal influenza in most countries with adequate surveillance.

The second is PANDEMIC SEVERITY INDEX The index focuses less on how likely a disease will spread worldwide-that is, become a pandemic-and more upon how severe the epidemic actually is.The main criterion used to measure pandemic severity will be case-fatality ratio (CFR), the percentage of deaths out of the total reported cases of the disease.The table is given below

Category	CFR
1	less than 0.1%
2	0.1% to 0.5%
3	0.5% to 1%
4	1% to 2%
5	2% or higher