A foodborne infection occurs when the pathogen itself makes its way into your food. In an infection, the food, along with the pathogen is ingested, and the organism itself is responsible for causing illness. Often, whether someone gets sick will depend on their underlying health and the number of the organism's cells ingested. Some organisms have the ability to make you sick with 8 ingested cells, while others require much larger numbers. We refer to this as the virulence factor. The fewer cells required to make you sick, the more virulent or "dangerous" the pathogen is. Sometimes, someone may show no noticeable symptoms but still carry an organism around and therefore be able to make others sick - we call this person a carrier.

One important group of bacteria that can cause foodborne illness include spore-forming bacteria - they pose a major threat to food safety. Bacterial spores are of concern to the food industry due to their ability to survive processing and disinfectant methods. They are resistant to heat and chemicals, therefore, once formed, they are difficult to eliminate, and chances of becoming ill increase. Hence, it is important to ensure good food handling practices are taken from the start to prevent spore formation in food.