Officials on Thursday were scrambling to find the source of listeria-contaminated deli meats and cheeses the have killed one person and sickened at least 15 others across six states.

Infections were reported in New York, Maryland, Illinois, Massachusetts, New Jersey and California. One death was reported in Maryland and one woman's pregnancy was lost because of an infection.

"It is difficult for investigators to identify a single food as the source of outbreaks linked to deli meats and cheeses," the Centers for Disease Control and Prevention said in a statement. "This is because listeria spreads easily between food and the deli environment and can persist for a long time in deli display cases and on equipment. A contaminated food likely introduced the outbreak strain into delis in multiple states."

The infections occurred between April 2021 and September 2022.

"The true number of sick people in this outbreak is likely higher than the number reported, and the outbreak may not be limited to the states with known illnesses," the CDC stated. "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 three to four weeks to determine if a sick person is part of an outbreak."

Five of those infected in New York reported purchasing deli meat at a NetCost Market in Brooklyn.

The CDC reported that 11 victims "are of Eastern European background or speak Russian."

Symptoms of listeria infections include diarrhea, nausea, severe headaches, high fever, poor balance, stiffness and stomach pain.

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