After touching another person or a pet. After touching your hair. Foodborne Illnesses Almost all foodborne illnesses are caused by bacteria. However, viruses, protozoa and trichinae are other microorganisms that may cause illnesses. Bacteria Bacteria are single celled organisms that take in food, produce waste and multiply very quickly.
Pathogenic bacteria is a group name for the bacteria that are capable of causing illness.
Some bacteria produce toxins in foods as they multiply. This toxin is very powerful and will cause illness and even death. Botulism toxin is the worst and most deadly. Other toxins will cause various degrees of illness which are almost always thought to be something other than food poisoning. Bacteria must have food, moisture and warmth to multiply.