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WHO Phases and UK alert levels

Phase	WHO international phases	Overarching public health goals
Inter-pandemic period
1	No new influenza virus subtypes detected in humans	Strengthen influenza pandemic preparedness at global, regional, national and sub-national levels Minimise the risk of transmission to humans; detect and report such transmission rapidly if it occurs
2	Animal influenza virus subtype poses substantial risk
Pandemic alert period
3	Human infection(s) with a new subtype, but no (or rare) person-to-person spread to a close contact	Ensure rapid characterisation of the new virus subtype and early detection, notification and response to additional cases Contain new virus or delay its spread transmission to gain time to implement preparedness measures, including vaccine development Maximise efforts to contain or delay spread, to possibly avert a pandemic and to gain time to implement response measures
4	Small cluster(s) with limited person-to-person transmission but spread is highly localised, suggesting that the virus is not well adapted to humans
5	Large cluster(s) but person-to-person spread still localised, suggesting that the virus is becoming increasingly better adapted to humans
Pandemic period
6	Increased and sustained transmission in general population UK alert levels: 1 Virus/cases only outside the UK 2 Virus isolated in the UK 3 Outbreak(s) in the UK 4 Widespread activity across the UK	Minimise the impact of the pandemic

Key:

Indicates current WHO phase

For more information WHO pandemic flu preparations and activities please visit their website [External website]