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Estimating Foodborne Illness: An Overview

Food safety is an important public health priority. Foodborne illness (sometimes called "foodborne disease," "foodborne infection," or "food poisoning) is a common, costly—yet preventable—public health problem. CDC estimates that each year roughly 1 in 6 Americans (or 48 million people) get sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases.

Estimates of foodborne illness serve as a foundation (or springboard) for future action by CDC, regulatory agencies, industry and others interested in improving food safety. They help us answer several important questions:

  1. How many foodborne illnesses occur? Burden of foodborne illness.
  2. Are they increasing or decreasing? Trends in foodborne illness.
  3. Which foods are responsible for foodborne illnesses? Attribution of foodborne illness.

The Importance of Estimating Foodborne Illness

Surveillance systems and surveys provide vital information but they do not capture every illness. Because only a fraction of illnesses are diagnosed and reported, we need periodic assessments of the total burden of illness to set public health goals, allocate resources, and measure the economic impact of disease. Therefore, we estimate. We use the best data available and make reasonable adjustments—based on related data, previous study results, and common assumptions—to account for shortcomings and missing pieces of information.

Documenting trends—which illnesses are decreasing and which are increasing—is essential for setting goals for prevention and for monitoring how well we are doing in reducing foodborne illness.

To prevent foodborne illness, food safety regulators, industry, and consumers need to know the major food sources for illness. By attributing the estimated number of foodborne illnesses to particular categories (also referred to as food “commodities”), we can target measures to prevent food contamination and set goals for improvement.

Burden of Foodborne Illness

Burden of foodborne illness tells us how many foodborne illnesses occur

Chart: Top pathogens contributing to domestically acquired foodborne illnesses and deaths, 2000 to 2008. Norovirus: Illnesses 58%; Deaths 11%. Salmonella, nontyphoidal: Illnesses: 11%; Deaths 28%. Clostridium perfringens: Illnesses: 10%. Campylobacter spp.: Illnesses: 9%; Deaths 6%. Staphylococcus aureus: Illnesses: 3%. Toxoplasma gondii: Deaths: 24%. Listeria monocytogenes: Deaths: 19%. .

Estimating illnesses, hospitalizations, and deaths for various types of diseases is a common and important public health practice. CDC estimates that each year roughly 1 in 6 Americans (or 48 million people) get sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases.

The 2011 estimates provide the most accurate picture yet of which foodborne bacteria, viruses, microbes ("pathogens") are causing the most illnesses in the United States, as well as estimating the number of foodborne illnesses without a known cause. These estimates are the first comprehensive estimates since 1999 and are the first ever to estimate illnesses cause solely by foods eaten in the United States.

Even with their limitations, estimates of disease burden are useful for understanding the magnitude of a public health problem. More about the 2011 estimates of foodborne illness.

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Trends in Foodborne Illness

Trends in foodborne illness tell if infections are increasing or decreasing

Surveillance systems and surveys provide vital information for assessing trends. Public health surveillance, such as that conducted by the Foodborne Diseases Active Surveillance Network (FoodNet), provides needed data for tracking trends. Documenting trends—which illnesses are decreasing and which are increasing—is essential for monitoring how well we are doing in reducing foodborne illness.

FoodNet, has given us snapshots of our progress in reducing Escherichia coli (E. coli) O157 and other foodborne infections since 1996. Each year, FoodNet reports on the changes in the number of people in the United States sickened with foodborne infections that have been confirmed by laboratory tests.

Foodborne diseases monitored through FoodNet include infections caused by the bacteria Campylobacter, E. O157, Listeria, Salmonella, Shigella, Vibrio, and Yersinia, and the parasites Cryptosporidium and Cyclospora.  The data collected by FoodNet also lets CDC, its partners, and policy makers know how much progress has been made in reaching national goals for reducing foodborne illness. More about trends in  foodborne illness.

Attribution of Foodborne Illness

Attribution of foodborne illness tells us which foods are involved

Determining the sources of foodborne illness is an important part of identifying opportunities to improve food safety. Having a

Chart: Contributions of different food categories to estimated domestically illnesses and deaths, 1998-2008*. Produce Illnesses - 46% Deaths - 23% ; Meat and Poultry Illnesses - 22% Deaths - 29%;Dairy and Eggs Illnesses - 20% Deaths - 15%; Fish and Shelfish Illnesses - 6.1% Deaths - 6.4%
better sense of the relationship between contaminated foods and illness supports food safety along the entire food production chain—from fields where food is grown to cutting boards in kitchens. Attribution estimates can be used to design new practices and prevention strategies to safeguard our food. For example, regulatory agencies can use attribution estimates to conduct risk analyses required in the rulemaking process.

Attributing illness to foods is a challenge for several reasons. There are thousands of different foods, and we eat many varieties even in a single meal. For the vast majority of foodborne illnesses, we do not know what food is responsible for someone getting sick.

One way we approach attribution estimation is to use  the data collected during foodborne outbreak investigations. Outbreak investigations provide direct links between foodborne illnesses and the foods responsible for them. Data from foodborne disease outbreaks are an important foundation to develop attribution estimates. To improve our understanding of the food sources of illnesses beyond outbreaks, however, additional data and analyses are needed. More about attribution of foodborne illness.

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