The most commonly recognized foodborne infections are those caused by the bacteria Campylobacter, Salmonella, E. coli O157:H7, and by a group of viruses called calicivirus, also known as the Norwalk and Norwalk-like viruses. 

Campylobacter is a bacterial pathogen that causes fever, diarrhea, and abdominal cramps. It is the most commonly identified bacterial cause of diarrheal illness in the world. These bacteria live in the intestines of healthy birds, and most raw poultry meat has Campylobacter on it.  Eating undercooked chicken or other food that has been contaminated with juices dripping from raw chicken is the most frequent source of this infection. 

Salmonella is also a bacterium that is widespread in the intestines of birds, reptiles, and mammals. It can spread to humans via a variety of different foods of animal origin. The illness it causes, salmonellosis, typically includes fever, diarrhea, and abdominal cramps. In persons with poor underlying health or weakened immune systems, it can invade the bloodstream and cause life-threatening infections. 

E. coli O157:H7 is a bacterial pathogen that resides in cattle and other similar animals. Human illness typically follows consumption of food or water that has been contaminated with microscopic amounts of cow feces.  The illness it causes is often a severe and bloody diarrhea and painful abdominal cramps, without much fever. In 3% to 5% of cases, a complication called hemolytic uremic syndrome (HUS) can occur several weeks after the initial symptoms. This severe complication includes temporary anemia, profuse bleeding, and kidney failure. 

The CDC estimates that that each year roughly 1 out of 6 Americans (or 48 million people) gets sick, 128,000 are hospitalized, and 3,000 die from foodborne diseases. The great majority of these cases are mild and cause symptoms for only a day or two. The most severe cases tend to occur in the very old, the very young, those who have an illness has already reduced their immune system function, and in healthy people exposed to a very high dose of an organism.