Foodborne illness is most often caused by bacterial agents, which may cause symptoms directly or produce toxins that cause disease. However, viral agents such as Norovirus and parasites such as Toxoplasma gondii can also cause foodborne illness. The most recent Centers for Disease Control and Prevention (CDC) estimates of the prevalence of different foodborne illnesses are from 2011. The CDC assessed the most common foodborne infections that cause illness and the most common foodborne infections that cause death. These statistics are for domestically acquired foodborne illnesses, or infections that are caught within the country. Traveling outside of the country puts a person at risk for other foodborne illnesses that are endemic to other parts of the world.
The most common foodborne infections that made people sick in 2011 were Norovirus, Salmonella, Clostridium perfringens, Campylobacter and Staphylococcus aureus. Norovirus caused over half of the reported foodborne illnesses. It is one of the most common foodborne illnesses, but it is not usually tested for in the laboratory because it is a virus and the tests are less available. The illness caused by Norovirus usually lasts a couple of days. Unlike most bacterial infections, it can be spread in contaminated food or from infected person to another person directly. Salmonella is a bacterium that can cause a localized infection or a more widespread infection that can be life-threatening. Campylobacter is a very common bacterial infection, usually originating from raw poultry. Clostridium perfringens is the most common Clostridium infection; botulism is also caused by a Clostridium species, but this is a relatively rare foodborne illness. Staphylococcus aureus is a common bacterium that can sometimes be a foodborne illness, especially when it produces a toxin that is ingested.
The top five causes of foodborne illness-related deaths are Salmonella, Toxoplasma gondii, Listeria monocytogenes, Norovirus and Campylobacter. Salmonella and Listeria infections can be very dangerous in people with compromised immune systems, because the infection can spread to other parts of the body. Toxoplasma gondii is a parasite that is often found in cat feces.
Other organisms can be a common source of outbreaks of foodborne illness. Certain strains of E. coli can cause foodborne illness. Shigella is a bacterium that causes diarrhea; Shigella is one of the major foodborne pathogens outside of the country, as are certain bacteria in the genus Vibrio.