PHILADELPHIA — The Centers for Disease Control and Prevention (CDC) is warning Americans about a listeria outbreak that has sickened more than two dozen people in 12 states. The outbreak is believed to be linked to processed meats.

As of Friday, 28 people have fallen ill, all of whom have been hospitalized, and two people have died: one from Illinois and one from New Jersey, the federal health agency said.

New York is the state with the most cases, with seven, followed by Maryland with six. States that have also reported cases include Illinois, Georgia, Massachusetts, Minnesota, Missouri, New Jersey, North Carolina, Pennsylvania, Virginia and Wisconsin.

“The actual number of people sick in this outbreak is likely higher than the reported number, and the outbreak may not be limited to states with known illnesses,” the CDC wrote in its update Friday. “This is because some people recover without medical care and are not tested for Listeria. In addition, recent illnesses may not yet be reported because it typically takes 3 to 4 weeks to determine whether an ill person is part of an outbreak.”

The CDC said it and its partners, including the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS), are collecting data to determine the source of the outbreak. Many of the patients in this outbreak reported eating sliced ​​meat from delis before they got sick.

There is currently no data to suggest that people become ill from pre-packaged meats.

“Of the 18 individuals who could be interviewed, 16 reported eating meat that had been cut in a deli, most commonly deli-cut turkey, liverwurst, and ham. Meat was cut in a variety of grocery stores and delis,” the CDC wrote.

Cases were reported between May 29 and July 5, according to CDC data. Patients range in age from 32 to 94, with a median age of 75. Overall, 72% of patients identified as white, 23% as black or African American, and 5% as Asian.

What are the symptoms?

When people eat food contaminated with the bacteria Listeria monocytogenes, it can cause a serious infection known as listeriosis. This can develop into invasive listeriosis, when the bacteria spread beyond the intestines to other parts of the body, the CDC says.

According to the CDC, symptoms of serious illness usually begin one to four weeks after eating the contaminated food, but they can occur the same day or as late as 70 weeks later.

An estimated 1,600 people get listeriosis each year, and about 260 people die. Those most at risk are pregnant women and newborns, adults 65 years of age or older, and people with weakened immune systems.

People who are not pregnant are likely to experience symptoms such as fever, headache, muscle aches, fatigue, stiff neck, confusion, or loss of balance. People who are pregnant are likely to experience only fever and flu-like symptoms.

The CDC advises people at higher risk for listeriosis not to eat meat sliced ​​at a deli unless it has been heated to an internal temperature of 165 degrees Fahrenheit or until it is steaming hot just before serving. The agency also recommends calling your health care provider if you have symptoms of listeriosis and have recently eaten sliced ​​meat from a deli.