Silence of evidence in the case of pandemic influenza risk assessment

During a pandemic, such as current H1N1 'swine flu', decisions are made with a sense of urgency. Yet, current policies emphasise the need to ground policies on evidence. This paper studies the tension that remains in decision-making processes when evidence is weak or 'silent' due to the sudden or unpredictable course of an event. The main focus is on the so-called 'known unknowns', factors of which we have only limited or weak evidence in the pandemic risk assessment processes. These processes cover, for example, monitoring the course of the pandemic, estimating the most affected age groups, and assessing population-level pharmaceutical interventions. This paper conceptualises the 'unknown' within these processes as silence of evidence. As the case of pandemic risk assessment shows, a new, emerging situation has not yet accumulated a robust body of evidence for decision making. These uncertainties are conceptualised as silent evidence. In a similar way, historical and archaeological studies acknowledge that there is evidence that is not yet discovered, interpreted or found. This paper develops a new way to look at unknown factors that affect risk assessment under a pandemic by focusing on the tension that remains in decision-making processes under pressure.