Two major food companies are voluntarily recalling products that contain spinach that may have been contaminated with Listeria prior to reaching their facilities. The products are not definitely known to be contaminated and so far no illnesses have been linked to eating the products . Still, with even a suspicion, a recall is the safest action. Full details about the involved products and how to return them are here at the FDA website.
My post on March 16, 2015 talks about symptoms and treatment of Listeriosis and another food recall