Listeriosis – United States

CDC, public health, and regulatory officials in several states, and the FDA are collecting different types of data to investigate a multistate outbreak of listeria infections.

Epidemiological data show that Hispanic-style fresh and soft cheeses may be contaminated with Listeria and may be making people sick. A specific type or brand of Hispanic-style fresh and soft cheese has not yet been identified.

As of 11 Feb 2021, 7 people infected have been reported from 4 states. Illnesses started on dates ranging from 20 Oct 2020, to 22 Jan 2021, with 6 recent illnesses in 2021.

The true number of sick people in an outbreak is likely higher than the number reported, and the outbreak may not be 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 be reported as it usually takes 2 to 4 weeks to determine whether a sick person is part of an outbreak.

Sick people range in age from 45 to 75 years, with a median age of 61. Six people are Hispanic, and 43% are female. All 7 people have been hospitalized. No deaths have been reported.

State and local public health officials are interviewing people about the foods they ate in the month before they got sick. Of the 4 people interviewed, 3 reported eating at least one type of Hispanic-style fresh and soft cheeses, and all 3 reported eating queso fresco. Public health officials are continuing to interview sick people to try to identify a specific type or brand of cheese.

Photo: Listeria monocytogenes.

Food items likely to be contaminated with Listeria include ready-to-eat refrigerated meat products, such as smoked salmon, sushi, and cold-cut meats that do not require further cooking before eating, refrigerated pates or meat spreads, unpasteurized (raw) milk and dairy products, such as soft cheeses, and raw fruits and vegetables (such as sprouts).

Even if initial contamination adds only a few Listeria organisms to the food, the contamination can be significant for refrigerated foods because the bacteria can multiply at refrigerator temperatures to a sufficient number to cause disease.

People at increased risk for disseminated listeriosis, which include pregnant women (and their newborns), adults aged 65 years or older, and people with weakened immune systems, should avoid eating food potentially contaminated with Listeria.

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 of the recalled products and developed symptoms of Listeria infection should seek medical treatment and tell their doctors about the possible Listeria exposure.

Also, anyone who has eaten of a recalled product 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 and other complications. 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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