1 Dead, 11 Hospitalized After Listeria Outbreak Linked to Packaged Salad, CDC Says All affected salads were processed in Springfield, Ohio, according to the CDC.

 -- A multi-state listeria outbreak has killed one person and hospitalized 11 others, according to the U.S. Centers for Disease Control and Prevention.

People have been sickened by the listeria bacteria in Michigan, Massachusetts, Indiana, New Jersey, Pennsylvania and New York, the CDC said today, noting that the largest reported outbreak so far has been in New York, where four people fell ill.

Listeria can be a notoriously difficult food-borne illness to track because the incubation period is between 3 days and 70 days. The bacteria can also survive colder temperatures in a fridge.

All 12 people reported ill were hospitalized, including one pregnant woman, the CDC said. Five people who were interviewed by the CDC said they had eaten packaged salad in the month before they became ill. Two people specified they had eaten a Dole brand of salad.

The illnesses were first reported on July 5, 2015, and the CDC started to investigate in September.

The Ohio Department of Agriculture reported that it found listeria bacteria in a test of the brand's "Field Greens" packaged salad. Dole said it is now withdrawing all salad products that were produced at the facility in Springfield, Ohio, and the CDC has advised consumers and restaurants to throw out the salad immediately.

In a statement sent to ABC News today, Dole officials said the withdrawal of the salad was being done "out of an abundance of caution" and in collaboration with the CDC and U.S. Food and Drug Administration. The company stressed no other Dole facilities are affected.

The packaged salads were sold under various brand names, including Dole, Fresh Selections, Simple Truth, Marketside, The Little Salad Bar, and President's Choice, according to the CDC. The packaged salads can be identified by the letter "A" at the beginning of the manufacturing code found on the package.

People most at risk of listeria infection are young children, the elderly, pregnant women or people with compromised immune systems. Symptoms include fever, muscle aches, headache, stiff neck, confusion or loss of balance, according to the CDC. The disease is especially dangerous for pregnant women, since it can lead to miscarriage, stillbirth, premature delivery, or infection of a newborn.

Of the estimated 1,600 people infected with the bacteria annually in the U.S., approximately 260 deaths occur due to listeriosis, according to the CDC.