Genomic Match Closes a Multi-Year Listeria Outbreak Traced to Requeson

TL;DR — A multi-year Listeria outbreak tied to Clover Hill Dairy's soft requeson cheese has sickened 9 people across 3 states, hospitalizing 8 and killing 1. The company recalled all its cheese and Maryland suspended its license.

Soft fresh cheese recurs in foodborne-illness investigations for structural reasons, and this case fits the profile. A Maryland dairy's requeson — a ricotta-style soft cheese common in Latin American cooking — has been tied to a Listeria monocytogenes outbreak that regulators date back years, with a casualty count that makes "possible contamination" language read as understatement.

Timeline

On June 5, 2026, Clover Hill Dairy of Mechanicsville, Maryland, voluntarily recalled all of its Soft Ricotta/Requeson Cheese, per the FDA. The product was distributed between May 4 and May 30, 2026, across North Carolina, New York, Virginia, Maryland, New Jersey, and Washington, D.C. The recall was subsequently widened to all of the company's cheese products. Regulatory action preceded the public recall: the Maryland Department of Health suspended the facility's operating license on May 30, 2026, and the company later agreed to pull its entire output.

The outbreak figures

As of June 9, 2026, the FDA and CDC reported a multi-state, multi-year outbreak:

• 9 people infected with the outbreak strain
• 3 states
• 8 hospitalized
• 1 death, in Maryland

The link is not circumstantial. Six product samples of requeson tested positive for Listeria monocytogenes and matched the outbreak strain — the genomic fingerprint that converts "this cheese might be involved" into "this cheese is the source." The "multi-year" framing is the most consequential detail: it indicates a contamination problem that persisted in the supply chain well before the cases were connected.

Why soft cheese, structurally

Listeria is unusual in that it proliferates under refrigeration — temperatures that arrest most bacteria. High-moisture fresh cheeses without a hard aging step are an ideal substrate, which is why public-health agencies repeatedly flag queso fresco, requeson, and similar styles for pregnant people, older adults, and the immunocompromised. The resulting infection, listeriosis, carries a case-fatality rate far above most foodborne pathogens and can incubate for weeks, making outbreaks slow to trace. Guidance for anyone holding Clover Hill cheese is direct: do not eat it, discard it, and sanitize anything it contacted.

The 2026 pattern

This is not an isolated event. Listeria drove several notable recalls and outbreaks in 2026, spanning deli meats to prepared pasta meals — evidence the pathogen keeps reaching the same vulnerable categories: ready-to-eat foods and soft dairy. The Clover Hill case is distinguished mainly by how cleanly the genomic evidence closed the loop, and by how long that loop apparently ran.

FAQ

What is requeson?

Requeson is a soft, fresh, ricotta-style cheese common in Mexican and other Latin American cooking. Like other high-moisture fresh cheeses, it offers little natural defense against Listeria, which is why it appears so often in dairy-linked outbreaks.

How do I know if cheese I bought is affected?

Clover Hill Dairy recalled all of its cheese products, distributed in NC, NY, VA, MD, NJ, and Washington, D.C. If you have any cheese from this Mechanicsville, Maryland company, the FDA's guidance is to discard it and clean surfaces it contacted, even if it looks and smells fine.

Who is most at risk from listeriosis?

Pregnant people, newborns, adults over 65, and anyone with a weakened immune system. Symptoms can include fever and muscle aches, and in pregnancy can lead to miscarriage or stillbirth — and may not appear until weeks after eating contaminated food.

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Sources: FDA Outbreak Investigation, FDA Recall Notice, CDC on Listeria.

Image: Lasagnolo9, CC BY-SA 4.0, via Wikimedia Commons.

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