Listeria may linger in your system without showing itself for up to two months after you're exposed. People with listeria infections tend to have fever, muscle aches, diarrhea, and nausea. If it spreads to the nervous system, you can also get a headache, lose your sense of balance, become confused, or have convulsions. Most people who report to the hospital with listeria already have systemic infections, meaning the bacteria have spread from the gut to the bloodstream. Once it's there, the listeria can also cause meningitis, which is the inflammation of the membranes and fluid around your brain. The only upside is that if you do have an infection, symptoms will inevitably appear, so report to your doctor if you might have been exposed and have any of the symptoms listed above (especially if you're pregnant or elderly).