Before revision:  This condition implies that behavioral responses are most likely to undermine public-health interventions near the peak of severe diseases . We also derive an explicit formula for the behavior of a heterogeneous population. A key difference from the homogeneous case is that high-risk individuals may choose to temporarily stop all activity when they are likely to encounter infected low-risk individuals .
After revision:  This condition implies that behavioral responses are most likely to undermine public-health interventions near the peak of severe diseases .