Expert judgments of pandemic influenza risks.

Structured surveys were conducted with 19 medical experts, and 17 non-medical experts in related fields, attending a meeting about pandemic influenza. Respondents gave quantitative judgments for key variables potentially affecting the extent of a possible H5N1 pandemic. The medical experts saw about a 15% (median) chance of efficient human-to-human transmission, in the next 3 years. Should it occur, they saw almost no chance of there being adequate vaccines or antiviral responses. They saw varying chances of six other mitigation strategies reducing the threat, expressing the greatest faith in improved surveillance. Compared to the medical experts, the non-medical experts saw much higher chances of both human-to-human transmission and of effective vaccine and antiviral responses being available. The medical experts and the non-medical experts had similar, dire predictions for the extent of casualties, should transmission occur in the next 3 years. Their responses to open-ended questions revealed some of the theories underlying these beliefs.