The Brief

Nine Listeria Cases, One Strain, Three Years Apart

Nine Listeria cases, one genetic strain, samples spanning March 2023 to May 2026, and an unopened tub of Clover Hill requeson that still carried the strain. A strain that recurs across three years is a resident living in the plant, not a one-time slip. You tell residents from transients by sequencing your own environmental positives, not by clearing one swab at a time.