In a nutshell: Bacteria and viruses are the most common causative agents of foodborne illnesses. Bacteria grow rapidly in foods that are warm, rich in moisture or protein and low in acidity. Milk, shell eggs, poultry, fish, meat and shellfish are common foods susceptible to bacteria growth. Although viruses cannot grow in food or water, a small number of viral particles can cause sickness when consuming the contaminated food.
Information on some of the most common bacteria and viruses that cause foodborne illnesses is provided below: