Federal officials say a Listeria outbreak that spanned a decade is over. Two people died as a result of their infections.

The Food and Drug Administration and the Centers for Disease Control and Prevention investigated the outbreak. It began in June 2014 and continued through December 2023. A total of 26 people in 11 states were confirmed as outbreak patients; 23 of them had to be hospitalized. Also, two people got sick during their pregnancy and one person had a pregnancy loss. There were also two newborns with Listeria infections.

Of 22 patients interviewed, 73 percent reported eating queso fresco, cotija, or other similar cheeses.

Epidemiologic and laboratory data showed that queso fresco and cotija cheese made by Rizo-López Foods made people sick in this outbreak. Many foods including cheeses, crema, and yogurts were recalled. Recalled foods are past their shelf life. See the FDA page for recall notices. All recalled products are past their use-by dates.

“The true number of sick people in this outbreak was likely higher than the number reported, and the outbreak may not have been limited to the states with known illnesses. This is because some people recover without medical care and are not tested for Listeria. In addition, recent illnesses may not yet have been reported as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak,” according to the CDC’s outbreak update.

Public health investigators used the PulseNet system to identify illnesses that may have been part of this outbreak. CDC PulseNet manages a national database of DNA fingerprints of bacteria that cause foodborne illnesses. DNA fingerprinting is performed on bacteria using a method called whole genome sequencing.

Whole genome sequencing showed that bacteria from sick people’s samples from 2014 to present are closely related genetically. This suggested that people in this outbreak got sick from the same food.

In January 2024, the Hawaii State Department of Health’s Food and Drug Branch collected a sample of aged cotija cheese product made by Rizo-López Foods during routine sampling. Testing identified the outbreak strain of Listeria in the product.

The FDA conducted inspections at the Rizo-López Foods facility and collected food and environmental samples for testing. FDA found the outbreak strain from two environmental samples that were collected at the facility.

About Listeria infections
Food contaminated with Listeria monocytogenes may not look or smell spoiled but can still cause serious and sometimes life-threatening infections. Anyone who has eaten any recalledproduct and developed symptoms of Listeria infection should seek medical treatment and tell their doctors about the possible Listeria exposure.

Also, anyone who has eaten any of the recalled products should monitor themselves for symptoms during the coming weeks because it can take up to 70 days after exposure to Listeria for symptoms of listeriosis to develop. 

Symptoms of Listeria infection can include vomiting, nausea, persistent fever, muscle aches, severe headache, and neck stiffness. Specific laboratory tests are required to diagnose Listeria infections, which can mimic other illnesses. 

Pregnant women, the elderly, young children, and people such as cancer patients who have weakened immune systems are particularly at risk of serious illnesses, life-threatening infections, other complications and death. Although infected pregnant women may experience only mild, flu-like symptoms, their infections can lead to premature delivery, infection of the newborn, or even stillbirth.

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