Each surveillance component is targeted at a particular susceptible population, for which conclusions will be made. In this step, surveillance designers should define this population in several steps detailed below.
3.1 Surveillance objective
The main surveillance objective for a component can, sometimes, be different from the overall main objective of the system, although the component will also contribute to the system objective.
3.2 Target species
Addressed in the surveillance components overview. Please see page “2-Overview of surveillance components”.
3.3 Target sector
Addressed in the surveillance components overview. Please see page “2-Overview of surveillance components”.
3.4 Sectors missed
Surveillance designers should consider other sectors/strata from the total susceptible population (defined in the surveillance scenario) which are not being covered by this particular component and list them, to later compare to sectors covered by other components. For example, if a surveillance system targets cattle and the current surveillance component addresses only dairy cattle, then part of the susceptible population is being missed, namely beef cattle and veal calves.
3.5 Geographical area covered
Addressed in the surveillance components overview. Please see page “2-Overview of surveillance components”
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3.6 Target criteria
This refers to whether there were any selection criteria used to choose this particular target population (if the target population for this component is not the entire susceptible population defined for the surveillance system). Criteria for selection could be for instance logistic/convenience (this component focuses on a particular sector of the population because they are easier to sample or more accessible); higher probability of infection; higher probability of showing clinical signs; feasibility of detection (the diagnostic tests available can only be used in animals above a certain age, or non-vaccinated animals); or higher severity of consequences in case of infection, which is the case for instance when surveillance is focused on breeder animals.
3.7 Percentage covered
This step considers whether there are any estimations of the percentage of the total susceptible population (defined in the surveillance scenario) covered by the target population defined for this specific component. This could be, for example, the percentage of the cattle population that is dairy for a component focused on dairy cows. Surveillance designers may need to consult national registries or national experts.
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