About how many cases of food-borne illness occur in the U.S. each year?

There’s a huge difference between number of confirmed cases and the estimated number of cases. If a patient is seen in a doctor’s office or hospital and the agent (the type of pathogen) is confirmed, the case must be reported to the Center for Disease Control. CDC records show over 2 million confirmed cases per year.
 
However, many people who develop a short-term food-borne illness do not consult a doctor, and, in many cases seen by a physician, the particular pathogen is never identified. A Harvard Medical School health report estimates that about 76 million cases of food-borne illness occur annually and about 5,000 deaths. Figuring the U.S. population at 307 million, that would be roughly 1 out of 4 Americans getting a food-borne illness each year!
 
The pathogens that cause food-borne illness are carried by livestock and poultry in their digestive tracts. It is nearly inevitable that some of the organisms will end up on the meat. Processors use antimicrobial sprays and “steam cabinets” to kill the organisms. However, since the original source of these organisms is the raw animal product itself, proper cooking is the last point in the chain where the potential for food-borne illness must be controlled. Some of these organisms have become more virulent because of the use of antibiotics in animal feed, which promotes the emergence of pathogens more resistant to the antibiotics prescribed for patients. However, these uses of antibiotics have been substantially limited or curtailed completely in the past 15 years.
 
Source(s):
Healthy Eating: a guide to the new nutrition edited by Frank M. sacks, M.D. Harvard Health Publications, 2008.
Food Borne Illness. Union of Concerned Scientists.
Centers for Disease Control and Prevention, Health Topics A to Z.