Every year, about 48 million Americans -- 1 in 6 -- get a food-borne illness. 

Often, the culprit food is a mystery.

Now, a new CDC report based on a decade of data offers the first comprehensive estimates of which foods are to blame.

Produce accounts for nearly half of the illnesses, and the norovirus is often to blame. Norovirus causes about 20 million cases of "stomach flu" each year. A new strain is going around the U.S.

Poultry is the food source with the most fatal infections. Salmonella and listeria are the common germs causing these infections.

"There is food-borne illness caused by a wide variety of foods," says researcher John Painter, DVM, an epidemiologist at the CDC.

"We didn't attempt to assign any risk for [specific] foods in the study," he says. The report does not mean people should avoid any foods, especially healthy choices such as produce, he says. The foods most often involved in outbreaks are often the foods we eat frequently and are part of a healthy diet.

The report is published in the journal Emerging Infectious Diseases.

According to the CDC, the report is the most complete effort to attribute illness to specific foods.

Food-borne Illness Report: Details

Food-borne illness sends 128,000 Americans to the hospital each year and kills 3,000 annually.

To compile the report, the CDC evaluated nearly 4,600 food-borne disease outbreaks from 1998 to 2008. The researchers had information on both the specific food causing the outbreak and the specific type of illness.

They estimated how much food-borne illness is accounted for in 17 food categories. Among the findings:

• Nearly half of illnesses were linked to produce. Produce includes fruits, nuts, leafy greens, and other vegetables.
• Of these produce foods, leafy greens were most often involved in food-borne illness. Norovirus was often the germ involved.
• Dairy was the second most frequent food source for infections.
• Contaminated poultry was to blame for the most deaths, involved in 19% of fatal cases. Many were linked to listeria and salmonella infections. Together, meat and poultry were to blame for 22% of illnesses and 29% of deaths.
• All 17 food categories were involved in some outbreaks, but the frequency for each category varied.
• Half of the outbreaks with a known food involved foods with ingredients from several food categories.
• Dairy and eggs accounted for 20% of illnesses and 15% of deaths.
• Fish and shellfish accounted for 6.1% of illnesses and 6.4% of deaths.

Food handlers are often to blame for norovirus outbreaks, according to a previous CDC study.

This virus is in the vomit and stool of infected people. It can be passed when infected food handlers don't wash their hands.

Preventing Food-borne Illness

Simple steps, both at home and when eating out, can lower your risk of food-borne illness. 

"Being careful of cross-contamination in the kitchen is one of the most important elements," Painter says.

For instance, slicing chicken on a cutting board, then using it to prepare a salad, raises infection risk.

Wash hands often, especially when preparing food, to cut down the risk of transmitting norovirus, Painter says.

Don Schaffner, PhD, a food microbiologist at Rutgers University who was not involved in the report, recommends that people wash raw food. "If you are buying your own produce, such as head lettuce, you want to wash it properly in your kitchen," he says.

However, if you buy the packaged, triple-washed products, he recommends against washing it again. The risk of contamination in your kitchen has been found to outweigh the risk of triple-washed lettuce making you sick.

Home cooks just getting over a bout of vomiting and diarrhea should not be handling food, Schaffner says.

When eating out, if you notice employees not washing their hands, report that to the manager or your local health department, Painter says. If many people get sick eating out after having the same meal, call the county health department.

"It's those outbreaks that are the basis of outbreak reports," he says.

Schaffner reports serving as a consultant to the food industry and for companies making hand sanitizer and antibacterial soaps.

SOURCES: Painter, J. Emerging Infectious Diseases, March 2013.John Painter, DVM, epidemiologist, CDC.Don Schaffner, PhD, professor of food microbiology, Rutgers University; science communicator, Institute of Food Technologists.

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