As of November 9, a total of 13 infected people had severe cases and required hospitalization, the CDC said in a statement. One person in Maryland died, and one pregnant person had a miscarriage as a result of a listeria infection. While the investigation is ongoing, many cases appear to be concentrated in New York, where five people with confirmed infections said they bought sliced deli meat or cheese from at least one location of NetCost Market, a grocery chain selling international foods, according to the CDC. So far, the CDC says public health investigators have identified a total of seven cases in New York, three in Maryland, two cases in Massachusetts, two cases in Illinois, and one case each in both Delaware and California. “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 said. “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.” Investigators are still working to identify any specific products or delis that may be contaminated with the outbreak strain. Public health officials don’t think that NetCost Market delis are the only source of the outbreak because many infected individuals didn’t shop there. No specific product has been identified as the source of the outbreak. To pinpoint the origins of the outbreak, state and local public health officials are interviewing infected individuals about the foods they ate over the month before they got sick, the CDC said. Out of 12 people interviewed so far, 11 reported eating meat or cheese from deli counters. The CDC advised people at higher risk of severe listeria illness to not eat meat or cheese from any deli counter, unless it is reheated to an internal temperature of 165 degrees F or until steaming hot. This includes people who are pregnant, 65 years and older, or who have a weakened immune system. The bacteria Listeria monocytogenes can cause a serious infection known as listeriosis. While many people have only brief, mild illness when they’re infected, high-risk individuals may develop severe infections in the bloodstream or brain that can be life-threatening. Many people with listeriosis will experience symptoms such as fever, muscle aches, headache, stiff neck, confusion, loss of balance, and convulsions, according to the CDC. Pregnant people may experience some flu-like symptoms, but are also at risk for miscarriage, stillbirth, premature deliveries, or life-threatening infections for their newborns. Listeriosis can be diagnosed with a simple lab test and treated with antibiotics. Foods responsible for listeria outbreaks have shifted over the years, according to the CDC. In the 1990s, most cases were linked to contaminated deli meats and hot dogs. These days, listeria is most often tied to dairy products and produce, with recent outbreaks traced to soft cheeses, celery, sprouts, cantaloupe, and ice cream.