A listeria outbreak possibly linked to fresh and soft cheeses has sickened seven people in four states, according to federal health officials.
In an investigation notice, the Centers for Disease Control and Prevention said officials were investigating a multistate outbreak of listeria monocytogenes infections linked to soft cheeses, which are made from pasteurized milk.
The CDC says a specific type or brand hasn’t been identified but says people at higher risk for severe listeria illnesses shouldn’t eat queso fresco, queso blanco and queso panela until the agency learns more. A recall hasn't been announced.
Those at higher risk for getting sick with listeria are pregnant women, adults 65 or older and people with weakened immune systems, the CDC said in a food safety alert, noting that if you are not in these groups, then "you are unlikely to get very sick from Listeria."
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As of information posted Feb. 12, there have been seven cases, four of them in Massachusetts. Connecticut, New York and Virginia have each had a case. All seven were hospitalized.
“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,” the CDC said.
Soft cheeses made from pasteurized milk have caused outbreaks in the past, the CDC notes.
"Although pasteurization of milk kills Listeria, products made from pasteurized milk can still become contaminated if they are produced in facilities with unsanitary conditions," the agency said.
The CDC says listeria can cause different symptoms, and invasive listeriosis usually starts one to four weeks after eating food contaminated with listeria but can start as late as 70 days after exposure.
Pregnant women typically experience fever and other flu-like symptoms. But infections during pregnancy also can lead to miscarriage, stillbirth, premature delivery or life-threatening infection of the newborn.
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Symptoms in people who are not pregnant can include headache, stiff neck, confusion, loss of balance and convulsions in addition to fever and muscle aches, the CDC said.
The Food and Drug Administration also is investigating.
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This article originally appeared on USA TODAY: Cheese warning: CDC says listeria outbreak could be tied to queso