Food & Wine A Multi-State Listeria Outbreak Linked to Deli Meats Killed 2 and Sickened 28 — Here’s What to Know and How to Keep Safe “It is important to note that it can take up to 70 days after exposure to listeria for symptoms of listeriosis to develop,” say Darin Detwiler, LPD, an associate teaching professor of food policy at Northeastern University and author of Food Safety: Past, Present, and Predictions.