Benefit-cost analysis of active surveillance of primary care physicians for hepatitis A.

We identified two random samples of 216 primary care physicians each. In one sample, we made weekly telephone contact for active hepatitis A (HA) surveillance; in the other, we made no such contact (passive surveillance). Appropriate county health departments were notified whenever we identified a HA case by active surveillance. Active surveillance was associated with a 2.8-fold increase in reported HA cases compared to passive surveillance. The estimated benefit: cost ratio active/passive surveillance was 2.5:1.