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[color=#000000][font=Times New Roman][color=#333333][font=Arial]Swine flu: UK planning assumptions
This document contains revised planning assumptions in relation to the current A(H1N1) Swine Flu pandemic. The assumptions are intended to assist local planning across all public and private sector organisations.
Planning assumptions are for both pan-UK and local areas, to take account of the potential variation in epidemic profile from one local area to another.
These assumptions are revised, reasonable worst case scenarios for planning purposes, based on what we have learned from the virus so far.
They are not predictions of how we expect the virus to behave. They support effective planning for every eventuality.
Document
Planning Assumptions for the First Wave of Pandemic Influenza
16 July 2009
Purpose
These planning assumptions relate to the current A(H1N1) epidemic and are appropriate for the first wave. They provide a common agreed basis for planning across all public and private sector organisations. Working to this common set of assumptions will avoid confusion and facilitate preparedness across the UK.
These planning assumptions are based on analysis and modelling of data from both inside and outside the UK. They will be kept under review, and are subject to change as further data become available on the current pandemic strain of Influenza.
There are a number of parameters each taken at their ‘reasonable worst case’ value. Taken together they represent a relatively unlikely scenario; they should therefore not be taken as a prediction of how the pandemic will develop. Planning against the reasonable worst case scenario will ensure, however, that plans are robust against all likely scenarios. Response arrangements must be flexible enough to deal with the range of possible scenarios up to the reasonable worst case and be capable of adjustment as they are implemented.
As further UK and international surveillance data emerges we will be looking to develop these planning assumptions and extend them beyond this period. It is possible that the virus may mutate, becoming more or less virulent, and it is important to remain prepared for the full range of possibilities. Therefore, any planning for future periods should be based on the standard reasonable worst case assumptions promulgated in pre-pandemic planning as set out in the ‘National Framework for responding to an influenza pandemic’ Chapter 3.
Timing and duration of the pandemic
It is unclear whether the pandemic will unfold as a single extended ‘wave’ or multiple waves separated by periods of reduced case numbers. At the current time, mid July 2009, the rate at which new cases accumulate is continuing to accelerate, consistent with an exponentially growing epidemic. If the current growth in cases is sustained, a substantial wave of cases with up to 30% of the population experiencing symptoms could peak in early September, although a smaller but earlier peak is also possible.
Alternatively, seasonal effects might substantially slow the epidemic in July and August – perhaps to the extent of leading to a decline in weekly cases in August, before resurgence in the autumn, for example when schools reopen. If so, the overall peak of the pandemic might be delayed to October or even later.
Geographic Spread
There may be a large variation in epidemic profile from one local area to another (even for a given overall clinical attack rate). The planning assumptions are thus shown both across the UK and for local areas where different1.
<sup>1 </sup><sup> Throughout this document a "local area" refers to a population of about 100,000 to 750,000. National refers to the UK population of about 62,300,000.</sup>3 of 6
<sup>
</sup>
Summary of the Planning Assumptions for the pandemic in 2009
<table dir="ltr" width="742" border="1" cellpadding="7" cellspacing="0"> <tbody><tr> <td colspan="2" valign="top" height="10">The tables below summarise the key planning assumptions. As noted above, this represents a "reasonable worst case" for which to plan, not a prediction. The first table covers the specific period until the end of August, while the second covers the first major wave of A(H1N1) infection more generally. They are explained in more detail in the supporting text below. All apply both across the UK and to local areas except where specific local assumptions are shown.2
Planning assumptions to August 31st 2009
</td> </tr> <tr> <td colspan="2" valign="top" height="10">Assumption
</td> </tr> <tr> <td valign="top" width="55%" height="9">Clinical Attack Rate
</td> <td valign="top" width="45%" height="9">
</td> <td valign="top" width="45%" height="9">
</td> <td valign="top" width="45%" height="9">
</td> <td valign="top" width="45%" height="9">
</td> <td valign="top" width="45%" height="10">
</td> <td valign="top" width="45%" height="9">
- Document type:Guidance
- Author:Department of Health
- Published date:16 July 2009
- Publication format:A4 electronic only
- Gateway reference:12229
- Pages:6
- Copyright holder:Crown
This document contains revised planning assumptions in relation to the current A(H1N1) Swine Flu pandemic. The assumptions are intended to assist local planning across all public and private sector organisations.
Planning assumptions are for both pan-UK and local areas, to take account of the potential variation in epidemic profile from one local area to another.
These assumptions are revised, reasonable worst case scenarios for planning purposes, based on what we have learned from the virus so far.
They are not predictions of how we expect the virus to behave. They support effective planning for every eventuality.
Document
Swine Flu
UK
Planning Assumptions
Issued 16 July 2009 2 of 6
Planning Assumptions for the First Wave of Pandemic Influenza
16 July 2009
Purpose
These planning assumptions relate to the current A(H1N1) epidemic and are appropriate for the first wave. They provide a common agreed basis for planning across all public and private sector organisations. Working to this common set of assumptions will avoid confusion and facilitate preparedness across the UK.
These planning assumptions are based on analysis and modelling of data from both inside and outside the UK. They will be kept under review, and are subject to change as further data become available on the current pandemic strain of Influenza.
There are a number of parameters each taken at their ‘reasonable worst case’ value. Taken together they represent a relatively unlikely scenario; they should therefore not be taken as a prediction of how the pandemic will develop. Planning against the reasonable worst case scenario will ensure, however, that plans are robust against all likely scenarios. Response arrangements must be flexible enough to deal with the range of possible scenarios up to the reasonable worst case and be capable of adjustment as they are implemented.
As further UK and international surveillance data emerges we will be looking to develop these planning assumptions and extend them beyond this period. It is possible that the virus may mutate, becoming more or less virulent, and it is important to remain prepared for the full range of possibilities. Therefore, any planning for future periods should be based on the standard reasonable worst case assumptions promulgated in pre-pandemic planning as set out in the ‘National Framework for responding to an influenza pandemic’ Chapter 3.
Timing and duration of the pandemic
It is unclear whether the pandemic will unfold as a single extended ‘wave’ or multiple waves separated by periods of reduced case numbers. At the current time, mid July 2009, the rate at which new cases accumulate is continuing to accelerate, consistent with an exponentially growing epidemic. If the current growth in cases is sustained, a substantial wave of cases with up to 30% of the population experiencing symptoms could peak in early September, although a smaller but earlier peak is also possible.
Alternatively, seasonal effects might substantially slow the epidemic in July and August – perhaps to the extent of leading to a decline in weekly cases in August, before resurgence in the autumn, for example when schools reopen. If so, the overall peak of the pandemic might be delayed to October or even later.
Geographic Spread
There may be a large variation in epidemic profile from one local area to another (even for a given overall clinical attack rate). The planning assumptions are thus shown both across the UK and for local areas where different1.
<sup>1 </sup><sup> Throughout this document a "local area" refers to a population of about 100,000 to 750,000. National refers to the UK population of about 62,300,000.</sup>3 of 6
<sup>
2 At present, the local assumptions differ from those for the UK only as regards the peak clinical attack rate. However, this may change as more evidence becomes available.
3 The 0.1% figure is based on experience outside the UK. Figures up to 0.35%, though unlikely, cannot be currently ruled out from UK data. </sup>
Summary of the Planning Assumptions for the pandemic in 2009
<table dir="ltr" width="742" border="1" cellpadding="7" cellspacing="0"> <tbody><tr> <td colspan="2" valign="top" height="10">The tables below summarise the key planning assumptions. As noted above, this represents a "reasonable worst case" for which to plan, not a prediction. The first table covers the specific period until the end of August, while the second covers the first major wave of A(H1N1) infection more generally. They are explained in more detail in the supporting text below. All apply both across the UK and to local areas except where specific local assumptions are shown.2
Planning assumptions to August 31st 2009
</td> </tr> <tr> <td colspan="2" valign="top" height="10">Assumption
</td> </tr> <tr> <td valign="top" width="55%" height="9">Clinical Attack Rate
</td> <td valign="top" width="45%" height="9">
5%-10%
</td> </tr> <tr> <td valign="top" width="55%" height="9">Peak clinical attack rate </td> <td valign="top" width="45%" height="9">
2-5% per week
</td> </tr> <tr> <td valign="top" width="55%" height="9">Complication rate </td> <td valign="top" width="45%" height="9">
15% of clinical cases
</td> </tr> <tr> <td valign="top" width="55%" height="9">Hospitalisation rate </td> <td valign="top" width="45%" height="9">
2% of clinical cases
</td> </tr> <tr> <td valign="top" width="55%" height="10">Case fatality rate </td> <td valign="top" width="45%" height="10">
0.1% of clinical cases3
</td> </tr> <tr> <td valign="top" width="55%" height="9">Peak Absence rate </td> <td valign="top" width="45%" height="9">
9% of workforce
</td> </tr> </tbody></table>