Multi-State Listeria Outbreak Linked to Maryland Dairy

The U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) are actively investigating a deadly multi-state outbreak of Listeria monocytogenes infections traced to soft cheeses produced by Clover Hill Dairy in Hagerstown, Maryland.

As of late June 2026, the outbreak has sickened 12 people across four states, with 10 hospitalizations and 1 death. Confirmed cases span Maryland, New York, Virginia, and Illinois. On June 18, 2026, Clover Hill Dairy issued a sweeping recall of all cheese products manufactured at its facility, including requeson (a ricotta-style soft cheese) sold under its own brand and potentially repackaged under labels such as KESSO and QUESOS LA RICURA.

FDA sampling proved devastating: six product samples and one environmental sample collected from the facility tested positive for Listeria monocytogenes. Whole genome sequencing confirmed that isolates from both the products and the environment were genetically identical to the outbreak strain found in patients. This dual-positive finding — product plus environment — highlights a critical vulnerability in dairy processing: Listeria can persist in cold, moist environments and cross-contaminate finished products even after pasteurization.

The Detection Gap: From Days to Minutes

Traditional Culture Methods

• 3–5 days from sample to confirmed result

• Require dedicated microbiology labs, incubators, selective media, and trained personnel

• Demand colony isolation, biochemical identification, and sometimes genetic confirmation

• Depend on cold-chain media storage and rigorous aseptic technique

• Results arrive too late to prevent distribution of contaminated batches

FSTest 21202 Listeria monocytogenes Rapid Test Kit (Lateral Flow)

• <24 hours total workflow — 10–15 minute visual readout after enrichment

• Zero specialized equipment — everything needed is in the kit

• Intuitive visual result — T-line indicates positive, C-line confirms validity; no interpretation training required

•  High specificity — no cross-reactivity with Salmonella, Shigella, E. coli, or other common pathogens

• Room-temperature stable — 18-month shelf life at 2–25°C; no cold chain needed for storage

•  Validated for complex food matrices — performs reliably in dairy, meat, seafood, beverages, and environmental swabs

About FSTest Co.,Ltd.

FSTest Co.,Ltd. is is a leading provider of rapid food safety testing solutions, serving food manufacturers, government inspectors, and third-party laboratories worldwide. With over three decades of R&D experience and ISO 9001-certified manufacturing, FSTest combines lateral flow innovation with rigorous quality standards to deliver detection solutions that are fast, simple, and trustworthy.

In an era where one environmental hotspot can trigger a multi-state recall and a fatal outbreak, FSTest empowers the food industry to move from reactive crisis management to proactive contamination prevention.