Listeriosis is one of the main zoonotic food-borne diseases, and although the number of cases is relatively low, its high mortality makes it a major public health problem. For the bacterium to cause disease, it is not enough for the food to be contaminated; it is also necessary for the pathogen to reach a certain concentration. As almost always happens in science, it is the dose that makes it poisonous.
Source:
phys.org