In the absence of sufficient numerical data, qualitative risk assessment is recognised as an important tool for providing risk managers with evidence-based predictions on which to formulate their decisions. Such approaches have been used in the area of animal health for import risk assessment for both livestock and zoonotic pathogens. Very few qualitative import risk assessments have, however, considered the aggregated probability of introduction, that is, the probability of at least one infected/contaminated entry per group of import units. Those that have are generally based on specific cases and do not follow a generic approach. In this paper, we consider whether or not it is feasible to develop a generic method and under what circumstances such an approach could be applied in practice. Our conclusion is that it would be difficult to specify a generic method because any such approach would rely on specifying numerical bounds for qualitative categories of probability as well as an idea of the number of imports and would thus be case-specific. As an alternative we propose a way of using case by case information to create a simple graphical reference tool which removes some of the subjectivity that is often associated with deriving qualitative risk. The reference tool considers various qualitative categories of individual probability and determines the relationship between this probability, the number of imports and the aggregated probability of entry. Applying the reference tool to a previously published case-study demonstrated some differences in conclusions and suggests that more subjective approaches can under-estimate probability and thus risk. It is concluded that this approach may be useful for future qualitative assessments of aggregated probability, provided that bounds for qualitative probabilities can be defined for the specific case situation.

在缺乏足够的数字数据的情况下，定性风险评估被认为是为风险管理人员提供基于证据的预测以制定决策的重要工具。此类方法已在动物健康领域用于评估牲畜和人畜共患病原体的进口风险。但是，很少有定性的进口风险评估考虑引入的总概率，即每组进口单元至少有一个被感染/污染的进入的概率。那些通常基于特定案例并且不遵循通用方法的协议。在本文中，我们考虑开发通用方法是否可行，以及在什么情况下可以在实践中应用该方法。我们的结论是，很难指定一种通用方法，因为任何此类方法都将依赖于为概率的定性类别以及输入数量的概念指定数值范围，因此将因情况而异。作为替代方案，我们提出了一种使用案例信息来创建简单的图形参考工具的方法，该工具消除了一些通常与得出定性风险相关的主观性。参考工具考虑各种概率的定性类别，并确定该概率，进口数量和进入的总概率之间的关系。将参考工具应用于先前发表的案例研究表明结论存在一些差异，并表明更多的主观方法可能会低估概率，从而降低风险。结论是，如果可以为特定案例情况定义定性概率的范围，则此方法可能对将来对合计概率的定性评估有用。