Issue a boil-water advisory or wait for definitive information? A decision analysis.

OBJECTIVE: Study the decision to issue a boil-water advisory in response to a spike in sales of diarrhea remedies or wait 72 hours for the results of definitive testing of water and people. METHODS: Decision analysis. RESULTS: In the base-case analysis, the optimal decision is test-and-wait. If the cost of issuing a boil-water advisory is less than 13.92 cents per person per day, the optimal decision is to issue the boil-water advisory immediately. CONCLUSIONS: Decisions based on surveillance data that are suggestive but not conclusive about the existence of a disease outbreak can be modeled.