Calculating food-specific attack rates (i.e., number of people who became ill after eating aparticular food divided by the total number who ate that food) is the most effective method to identify the probable source of infection in a known cohort outbreak.

Toronto Notes 2023 – Public Health, Outbreak Investigations:

“Foodborne outbreaks are best analyzed using food-specific attack rates to determine associations between individual foods and illness.”

MCCQE1 Objectives – Preventive Medicine > Epidemiologic Principles:

“Candidates must use epidemiologic tools, such as attack rates, to identify probable sources during outbreak investigations.”

Cohort study (C) is also acceptable but more time-intensive. Stool and food cultures (B, D) confirm the pathogen but not the source. HACCP (E) is a preventive method, not a tool for outbreak investigation.

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