WHO Pandemic Phases
The World Health Organization (WHO) has defined phases in the evolution of an influenza pandemic which allow a step-wise escalating approach to preparedness planning and response leading up to declaration of the onset of a pandemic. Once a pandemic has been declared, UK action will depend on whether cases have been identified in the UK, and how extensively it has spread. For UK purposes, therefore, additional UK alert levels are included within the WHO pandemic phase (Phase 6).
The WHO will announce the various phases as soon as they are confirmed, indicating the level of preparedness expected of WHO and its individual Member States. National Authorities are expected to be prepared to activate their national contingency plans following announcement of WHO Phase 5 (the highest pandemic alert level). Before announcing this phase, WHO will have consulted international experts to rule out other possible explanations, such as subversive activity. WHO will normally consult internationally before confirming Phase 6, i.e. the onset of a pandemic.
Transition Between Phases
Transition between phases may be rapid and the distinction blurred. The crucial interval is between WHO Phases 5 and 6, which will determine to a large extent whether vaccine can be developed in time for the first wave of illness in the UK
A move to a higher alert level may be triggered, after assessing the risk, if influenza due to a pandemic strain is affecting another country geographically close to the UK, although technically it is still ‘outside the UK’.
The World Health Orgaisation Pandemic Health Chart is available for download.
