Aftenposten reported Friday that two patients at the National Hospital in Oslo, Norway, died as a result of an infection linked to listeria and another 12 have been sickened since Oct. 1.

Hospital officials were cited as saying the source of the bacteria has not yet been pinpointed, but they said it may have come from contaminated cold food, possibly cheese. All refrigerated food at the hospital has been discarded, but officials said new cases may still arise as the bacteria’s incubation period can last for up to a month.

Pregnant women, newborns and adults with weakened immune systems are especially susceptible to listeria. A recent Australian study found that over half of expectant mothers received no information about the risks associated with listeria and certain foods.

The U.S. Centers for Disease Control recommendations for persons at high risk, such as pregnant women and persons with weakened immune systems, includes:

-Do not eat hot dogs, luncheon meats, or deli meats, unless they are reheated until steaming hot.

-Avoid getting fluid from hot dog packages on other foods, utensils, and food preparation surfaces, and wash hands after handling hot dogs, luncheon meats, and deli meats.

-Do not eat soft cheeses such as feta, Brie, and Camembert, blue-veined cheeses, or Mexican-style cheeses such as queso blanco, queso fresco, and Panela, unless they have labels that clearly state they are made from pastuerized milk.

-Do not eat refrigerated pâtés or meat spreads. Canned or shelf-stable pâtés and meat spreads may be eaten.

-Do not eat refrigerated smoked seafood, unless it is contained in a cooked dish, such as a casserole. Refrigerated smoked seafood, such as salmon, trout, whitefish, cod, tuna or mackerel, is most often labeled as "nova-style," "lox," "kippered," "smoked," or "jerky." The fish is found in the refrigerator section or sold at deli counters of grocery stores and delicatessens. Canned or shelf-stable smoked seafood may be eaten.