Food poisoning can be either a virus or bacteria.

Though bacteria and viruses are the most common sources of food poisoning, it can also be caused by parasites, mold, toxins, contaminants, and allergens.

Bacteria

Bacteria is responsible for a good number of food poisoning cases every year. Common bacteria contaminants include Salmonella spp., Staphylococcus aureus, Campylobacter jejuni, Listeria, Escherichia coli and Clostridium botulinum.

Viruses

Viruses can infect food and cause illness as well and include Hepatitis A, Hepatitis E, Rotavirus, and the Norwalk virus group.

Parasites

Common foodborne parasites include protozoa, tapeworms, and roundworms. The parasite that causes the most hospitalization in the US is Toxoplasma gondi, which causes toxoplasmosis. Additional parasites include Giardia intestinalis, Cryptosporidium paryum, Cyclcospora cayetanensis, Trichinella spiralis, and Taenia saginata. Foodborne illnesses caused by parasites include giardiasis, cryptosporidiosis, cyclosporiasis, trichinellosis, and Taeniasis.

Mold, Toxins, and Contaminants

Though not all mold is toxic, such as that found on some cheeses, some mold is highly toxic and can cause food poisoning. Food can also be contaminated with chemical substances that can cause food poisoning such as pesticides or melamine. There are plenty of natural toxins that can be found in food as well such as those found in pufferfish, wild mushrooms, and shellfish.

Find a Full List of Food Contaminants at the US Food and Drug Administration's Bad Bug Book website.