According to James E. Rogers, PhD, director of food safety testing and acting director of product testing at CR, it is unusual to have a strain of bacteria persisting for many years as in the case of this recall. He explains that listeria is a robust pathogen and once it enters a facility, it is difficult to eradicate.
An FDA spokesperson informed CR that listeria can easily spread from contaminated equipment or surfaces to food. If the source of contamination is not identified, it can persist for years, continuing to contaminate food and cause illness.
For most people, listeriosis, the infection caused by listeria, is likely to resolve on its own. The symptoms, including fever, muscle aches, nausea, vomiting, and diarrhea, can onset shortly after consuming contaminated food or up to two weeks later (more information).
However, for 1 in 20 people, the infection can become more severe and develop flu-like symptoms such as fatigue, headaches, and a stiff neck, as per the CDC. Additional symptoms may include confusion, loss of balance, and seizures. The CDC estimates that 1,600 people contract listeriosis each year, resulting in about 260 deaths.