The CDC said many people in the outbreak reported eating meat sliced at deli counters prior to getting sick. Twenty eight people have been infected in 12 states, including Illinois. All were hospitalized.
One person died in Illinois and one died in New Jersey.
One other person in Illinois fell ill.
The CDC said most people who became ill ate deli-sliced turkey and liverwurst from supermarkets and grocery store delis.
The agency could not yet pinpoint which meat was the source of the outbreak.
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Data was collected from May 29 to July 5, the CDC said.
The CDC said the true number of sick people is likely higher than the number reported.
But those who fell ill were from New York, Maryland, Georgia, Massachusetts, Missouri, New Jersey, Virginia, Illinois, Minnesota, North Carolina, Pennsylvania and Wisconsin.
The CDC said those who are pregnant, 65 or older or have a weakened immune system should avoid deli counter meat unless it is reheated to an internal temperature of 165 degrees.
They should also clean their refrigerators, containers and surfaces that may have touched deli meat.
Symptoms of Listeria can include fever, muscle aches and tiredness. They may also include a headache, a stiff neck, confusion, loss of balance or seizures.