Institute for Food Safety at Cornell University

Food Safety Virtual Office Hours: What Happens During a Foodborne Outbreak Investigation?

The virtual office hour, hosted by the New York State Department of Health and industry experts, dissected the step‑by‑step process of a foodborne outbreak investigation, from initial detection to regulatory action. Panelists explained how whole‑genome sequencing (WGS) now flags clusters of identical pathogen strains, turning sporadic cases into actionable alerts for public health agencies. Key insights covered the three‑phase workflow: (1) identifying a clinical cluster via WGS and temporal patterns; (2) conducting epidemiologic interviews to pinpoint a likely vehicle, such as leafy greens or onions; and (3) performing trace‑back analyses to locate the upstream source, often a distribution center or farm. When epidemiologic evidence is compelling, agencies may request a recall even before any food sample tests positive. Illustrative examples included a 31‑case leafy‑green outbreak where 96% of patients reported the same farm product, and a larger onion‑related incident affecting 380 people. The discussion highlighted that environmental or product testing can provide the “smoking gun” by matching the outbreak strain, but negative results do not automatically exonerate a facility. Retrospective investigations may also start from non‑human isolates found in databases, prompting renewed case interviews. The session underscored the heightened responsibility for food manufacturers to maintain rapid communication channels with FDA and CDC, as alerts can arrive within 12 hours. Preparedness—through robust traceability, WGS integration, and swift corrective actions—has become essential for protecting public health and limiting costly recalls.