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Annex B
Risk periods This section uses the concept of risk periods that is found in published literature on disease outbreaks, but expands it to illustrate the importance of planning to decrease the probability and impact of incursions. The time period before and during the incursion of a disease can be split into several critical risk periods. Actions taken, before and during these, affect the size of the epidemic and the impact of the disease incursion. The concept of a high-risk period (HRP) has been used when discussing the incursion of a transboundary disease. This is the period between introduction of a disease and the full implementation of effective measures to control spread. The length of this period is critical in determining the scale and duration of an epidemic. The HRP has been further subdivided into HRP1 and HRP2. HRP1 is the time between the first infection and first detection of the disease, the period of “silent spread”. HRP2 is the period between first detection and when control measures are put into effect. HRP2 represents the initial stages of controlling an already disclosed incursion. It is possible to add further periods before first infection. The low-risk period (LRP) is the period in which measures are applied to prevent incursion and routine surveillance for detection. This is also sometimes referred to as “peacetime” and is the status quo. In some cases, where the disease is present nearby or in the countries of trading partners, there may be a raised-risk period (RRP) during which a greater risk of introduction is recognized, and this should lead to heightened import and border controls, a campaign to raise awareness and increased vigilance. This gives four periods that are illustrated in Figure 5 below: There are different objectives during each of these periods and activities to achieve them, as indicated below: FIGURe 5
Risk periods
LRP
RRP
HRP1
HRP1
Low Risk Period
Raised Risk Period
High Risk Period 1
High Risk Period 2
The “status quo”, peacetime
Increased risk of introduction
Time between first infection and detection
Time between first detection and effective implementation of controls
