The contribution of residents who cooperate with ring-vaccination measures against smallpox epidemic.

OBJECTIVES: Establishing containment measures against the potential spread of the smallpox virus has become a major issue in the public health field since the 2001 anthrax attacks in the United States. The primary objective of the study was to investigate the relationship between the level of activity of public health agencies and the voluntary cooperation of residents with ring-vaccination measures against a smallpox epidemic.

METHODS: A discrete-time, stochastic, individual-based model was used to simulate the spread of a smallpox epidemic that has become a more pressing topic due to 9/11 and to assess the effectiveness of and required resources for ring-vaccination measures in a closed community. In the simulation, we related sensitive tracing to the level of activity of the public health agency and strict isolation to the level of voluntary cooperation from residents.

RESULTS: Our results suggest that early and intensive case detection and contact tracing by public health agencies can reduce the scale of an epidemic and use fewer total resources. In contrast, voluntary reporting by the traced contacts of symptom onset after vaccination had little impact on the scale of epidemic in our model. However, it reduced the total required resources, indicating that citizens' voluntary cooperation would contribute to reducing the burden on public health agencies.

CONCLUSIONS: We conclude that a combined effort on the part of public health agencies and residents in performing containment measures is essential to quickly ending a smallpox epidemic.