Infected pets may display symptoms such as mild to severe diarrhea, anorexia, fever, nervous, muscular and respiratory signs, miscarriage, depression, shock and death. Listeria infection in humans can cause miscarriages, stillbirths, premature delivery, or life-threatening infection of the newborn in pregnant women. Healthy individuals may suffer only short-term symptoms such as high fever, severe headache, stiffness, nausea, abdominal pain, and diarrhea.