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Trends in Foodborne Illness in the United States

Estimates of burden of illness are designed to give the most accurate count of illnesses at a specific point in time. They are not intended to show disease trends—whether illnesses are increasing or decreasing.

Surveillance systems like FoodNet* (Foodborne Diseases Active Surveillance Network), America's report card for food safety, capture data over a period of time and are better at showing disease trends.

Figure: This figure depicts the relative rates by year of culture-confirmed infections with Campylobacter, Shiga toxin-producing Escherichia coli (STEC O157), Listeria, Salmonella, and Vibrio compared with 2006–2008 rates. Data for 2006–2013, provided by the Foodborne Diseases Active Surveillance Network on infections in the United States, indicate the relative change in the incidence of that pathogen compared with 2006–2008. The actual incidences of these infections cannot be determined from this figure. In 2009, the relative rate of Campylobacter was 1.02; in 2010, the relative rate was 1.06; and, in 2011 through 2013, the relative rate was 1.13. In 2009, the relative rate of STEC O157 was 0.76; in 2010, the relative rate was 0.72; in 2011, the relative was 0.74; in 2012, the relative rate was 0.89; and in 2013, the relative rate was 0.91. In 2009, the relative rate of Listeria was 1.2; in 2010, the relative rate was 0.99; in 2011, the relative rate was 1.08; in 2012, the relative rate was 0.95; and in 2013, the relative rate was 0.97. In 2009, the relative rate of Salmonella was 0.95; in 2010, the relative rate was 1.09; in 2011, the relative rate was 1.05; in 2012, the relative rate was 1.03; and in 2013, the relative rate was 0.96. In 2009, the relative rate of Vibrio was 1.21; in 2010, the relative rate was 1.39; in 2011, the relative rate was 1.16; in 2012, the relative rate was 1.44; and in 2013, the relative rate was 1.75

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Documenting trends in foodborne illness—which illnesses are decreasing and which are increasing—is essential to the overall goal of reducing foodborne illness.

  • 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

Each year, FoodNet reports on the changes in the number of people in the United States sickened with foodborne infections from these pathogens that have been confirmed by laboratory tests. This annual report card also lets CDC, its partners, and policy makers know how much progress has made in reaching national goals for reducing foodborne illness.

FoodNet: American's report card for food safety

Chart: FoodNet's Progress Report on six key pathogens For 2013: Percentage Change in 2013 compared to 2006-2008: Campylobacter-13% increase, E. coli O157-no change, Listeria-no change, Salmonella-no change, Vibrio-75% increase, Yersinia-no change

Highlights of 2013 FoodNet trend data

FoodNet collects and monitors information on laboratory-confirmed illnesses for about 48 million people—or, about 15 percent of the American population. FoodNet data provide the best measure of trends in foodborne disease in the United States. The 2013 data showed that foodborne infections continue to be an important public health problem in the United States and highlight the need to move forward with preventive measures.

  • FoodNet identified 19,056 cases of culture-confirmed bacterial and laboratory-confirmed parasitic infection, 4,200 hospitalizations, and 80 deaths among 48 million residents of 10 states (15% of the US population).
    • The most frequent infection was caused by Salmonella accounting for 38% of reported infections, and the second by Campylobacter (35%).  Vibrio accounted for 1.3% of reported infections.
  • Although the incidence of Salmonella infection (15.19 per 100,000 population) was lower in 2013 than in 2010–2012, it remains similar to 2006–2008, well above the national Healthy People objective (11.4 cases per 100,000 population)
    • Among serotyped Salmonella isolates, the top serotypes were Enteritidis, 1,237 (19%); Typhimurium, 917 (14%); and Newport, 674 (10%)
    • The incidence of serotype Enteritidis infection was lower in 2013 than in 2010–2012, but not than in 2006–2008. This may be partly explained by the large Enteritidis outbreak linked to eggs in 2010.
  • The incidence of Vibrio infections (0.51 per 100,000 population) was higher in 2013 than 2010–2012 and 2006–2008.
    • Among speciated Vibrio isolates, the majority were Vibrio parahae­molyticus (62%)
    • During the summers of 2012 and 2013, infections with a particular strain of V. parahaemolyticus serotype O4:K12 were associated with consuming shellfish from several Atlantic coast harvest areas. Before 2012, infections of serotype O4:K12 had not been associated with shellfish outside the Pacific Northwest region of the United States.
  • Diagnostic practices are changing.  New culture independent diagnostic tests (CIDTs) are increasingly used by clinical laboratories to diagnose bacterial enteric infections.  These tests do not by themselves isolate a living germ in a laboratory culture that can be further studied.
    • FoodNet has begun tracking the use of these new diagnostic tests, so that we can better understand their uptake. To date these tests are mostly being used for Campylobacter and STEC. 
    • In addition to culture-confirmed bacterial infections reported in FoodNet, there were 1,487 reports of positive CIDTs that were not confirmed by culture, either because the specimen was not cultured or because a culture did not yield the pathogen. These were not counted in the rates that are reported.

Highlights of 2012 FoodNet trend data

Data from FoodNet, which monitors 15% of the US population, provide the best measure of trends in foodborne disease in the United States. Overall, the 2012 FoodNet data showed a lack of recent progress in reducing foodborne infections and highlight the need for improved prevention.

  • FoodNet identified 19,531 laboratory-confirmed cases of infection.
    • The incidences of laboratory-confirmed CampylobacterCryptosporidiumSalmonella, Shiga toxin-producing Escherichia coli (STEC) O157 and non-O157, Shigella, and Yersinia infection were highest among children aged <5 years.
    • The incidences of Listeria and Vibrio infection were highest in adults aged ≥65 years.
  • The incidences of laboratory-confirmed Listeria, Salmonella, Shiga toxin-producing Escherichia coli (STEC) O157, and Yersinia infection did not change significantly in 2012 compared with 2006–2008.
  • Campylobacter was the second most common infection reported in FoodNet (14.3 cases reported per 100,000 population). Incidence of infection was 14% higher in 2012 compared with 2006–2008.
    • Campylobacter infections are usually self-limited, but may result in severe complications such as Guillain-Barré syndrome (a type of paralysis) and arthritis.
    • Exposures related to Campylobacter infection include consumption of undercooked poultry, raw milk, produce, and untreated water, and contact with young animals.
  • Vibrio infections are rare (0.41 cases reported per 100,000 population). Incidence of Vibrio infection was 43% higher in 2012 compared with 2006–2008.
    • Some types of Vibrio infections are often serious.
    • Many Vibrio infections are acquired by eating raw oysters. These infections are most common during warmer months, when waters naturally contain more Vibrio organisms.
    • Infections can be prevented by thoroughly cooking oysters and by not exposing wounds to bodies of warm seawater.
  • As a group, the incidence of infection with six key pathogens transmitted commonly through food (Campylobacter, Listeria, Salmonella, E. coli O157, Vibrio, and Yersinia) was not significantly different in 2012 than in 2006–2008.
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Long-term Trends

Comparison with the first three years of FoodNet surveillance (1996–1998) shows some clear changes:

 

  • The incidence of infections caused by CampylobacterListeria, STEC O157, Shigella, and Yersinia has declined, mostly in the first few years.
  • The overall incidence of Salmonella was unchanged, but the incidence of some types of Salmonella have increased while others have decreased.
  • The incidence of Vibrio infection is now 116% higher.
  • The overall incidence of infection with six key foodborne pathogens (Campylobacter, Listeria, Salmonella, STEC O157, Vibrio, and Yersinia) was 22% lower.
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Recent Efforts and Next Steps

Most foodborne illnesses can be prevented. Some progress has been made in decreasing contamination of some foods and reducing illness caused by some pathogens.  Recent efforts to reduce contamination of food and prevent these illnesses include:

  • Establishment in 2011 of performance standards for Campylobacter contamination of whole broiler chickens in processing plants.
  • Approval of more stringent time and temperature controls for oysters after harvest to prevent Vibrio vulnificus infections.
  • The Food Safety Modernization Act of 2011: It gives FDA additional authority to regulate food facilities, establish standards for safe produce, recall contaminated foods, oversee imported foods, and which requires improvements in surveillance and response to outbreaks. It calls on CDC to strengthen surveillance and outbreak response.

More can be done. Determining where to target prevention efforts that will reduce foodborne infections requires continued collection of information to understand sources of infection, implementation of measures known to reduce food contamination, and development of new measures.

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Highlights of 2011 FoodNet trend data

In 2011, the overall incidence of infection with six key pathogens transmitted commonly through food (Campylobacter, Listeria, Salmonella, Escherichia coli O157), Vibrio, and Yersinia) was not significantly different than in 2006–2008.

Chart: FoodNet's 2011 Progress Report on six key pathogens For 2011: Percentage Change in 2011 compared to 2006-2008:Campylobacter-14% increase, E.Coli 0157-25% decrease, Listeria-no change, Vibrio-no change, Yersinia-no change

Highlights of the 2011 FoodNet Report Card

Progress over time: Recent trends

Data released through FoodNet comparing 2011 with 2006–2008, rates of infection were significantly lower for Shigella (43% decrease) and E. coli O157 (25% decrease) and higher for Campylobacter (14% increase); incidence did not change significantly for Cryptosporidium, Listeria, Salmonella, Vibrio, and Yersinia infections.

  • Incidence was calculated by dividing the number of laboratory-confirmed infections in 2011 by U.S. Census estimates of the population of the FoodNet surveillance area.

Progress over Time: Long-term Trends

In contrast, the overall incidence of infection with six key pathogens transmitted commonly through food was significantly lower in 2011 compared with 1996–1998.

For individual pathogens, the incidence of infection was significantly lower in 2011 compared with 1996-1998 for Shigella (65% decrease), Yersinia (52% decrease), E. coli O157 (42% decrease), Listeria (35% decrease) and Campylobacter (22% decrease) but was higher for Vibrio (76% increase). It did not change significantly for Salmonella or Cryptosporidium.

Who is at Greater Risk of Foodborne Illness?

  • The incidences of laboratory-confirmed infection with Campylobacter, Cryptosporidium, Salmonella, Shiga toxin-producing Escherichia coli (STEC) O157 and non-O157, Shigella, and Yersinia were highest among children aged <5 years. The incidences of Cyclospora, Listeria, and Vibrio infection were highest among adults aged ≥65 years.
  • Young children and older adults were also more likely to have severe complications or die from these illnesses. Thirteen percent of infections, 24% of hospitalizations, and 57% of deaths occurred among adults aged ≥65 years.

Highlights of 2010 FoodNet trend data

Data released in CDC's Morbidity and Mortality Weekly Report [MMWR] summarizes 2010 data from FoodNet and provides the best measure of trends in foodborne disease from 1996–2010. It confirms that Salmonella infection has not declined in 15 years, but also shows that progress has been made in reducing several foodborne infections, for example:

  • Infection caused by a common type of E. coli (Shiga toxin–producing Escherichia coli O157), known as E. coli O157 has declined significantly (Figure 1). In fact, it was the only one of the nine infections tracked to reach the 2010 national health objective target.
  • As a group, infections caused by six key pathogens in 2010 were 23% lower, including

The FoodNet 2010 data showed a lack of progress in reducing infections caused by Salmonella and Vibrio.

  • Salmonella was the most common infection (1.2 million U.S. illnesses annually) and the most common cause of hospitalization and death tracked by FoodNet.
    • Infections have actually increased since 2006—2008 (Figure 1).
    • In 2010, the incidence of Salmonella was nearly three times the 2010 national health objective target.
    • Salmonella can contaminate a wide range of foods. There are many different types of Salmonella, and each type tends to have different animal reservoirs and food sources, making control challenging.
  • Incidence was higher for Vibrio infection (115% increase).
    • Vibrio infections are rare, but often serious, and are caused by eating contaminated seafood or exposing an open wound to seawater. Continued Vibrio illnesses highlight the lack of implementation of available control
      measures.

Overall, the FoodNet 2010 report shows a downward trend in foodborne infections, which is due, at least in part, to:

  • Enhanced knowledge about preventing contamination. PulseNet, the national molecular subtyping network for foodborne bacterial pathogens, can detect widely dispersed outbreaks and has greatly improved the detection and investigation of multistate outbreaks.
  • Cleaner slaughter methods, microbial testing, and better inspections in ground beef processing plants.
  • Regulatory agency prohibition of contamination of ground beef with E. coli O157 (resulting in 234 beef recalls since E. coli O157 was declared an adulterant in ground beef in 1994).
  • Improvements in the FDA model Food Code.
  • Increased awareness in food service establishments and consumers' homes of the risk of consumption of undercooked ground beef.

Other important pathogens transmitted commonly through food (e.g., norovirus, Clostridium perfringens, and Toxoplasma) are not tracked in FoodNet because tests to detect them are not generally available for clinical laboratories. Many of the control measures that would decrease illness caused by pathogens tracked in FoodNet would also decrease illnesses caused by pathogens not tracked presently.

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Figure 1. Relative rates of laboratory-confirmed infections with Campylobacter, E. coli O157, Listeria, Salmonella, and Vibrio, compared with 1996--1998 rates, by year --- Foodborne Diseases Active Surveillance Network, United States, 1996--2010*

Relative rates of laboratory-confirmed infections with Campylobacter, STEC1 O157, Listeria, Salmonella, and Vibrio compared with 1996–1998 rates, by year — Foodborne Active Surveillance Network, United States, 1996–2009

Abbreviation: STEC = Shiga toxin--producing Escherichia coli O157.

* The position of each line indicates the relative change in the incidence of that pathogen compared with 1996--1998. The actual incidences of these infections cannot be determined from this graph. Data are preliminary.

Figure 2. Changes in incidence of laboratory-confirmed bacterial infections, United States, 2010 compared with 1996–1998

Changes in incidence of laboratory-confirmed bacterial infections, United States, 2009 compared with 1996–1998(data are preliminsary). Yersinia=53% decrease,Vibrio=85% increase, STEC 0157(Shiga toxin-producing Escherichia coli=41% decrease, Shigella=55%decrease, Salmonella=10%decrease, Listeria=26%decrease, Campylobacter=30%decrease

*Foodborne Diseases Active Surveillance Network, referred to as FoodNet, is a surveillance system that collects information from sites in 10 states (Connecticut, Georgia, Maryland, Minnesota, New Mexico, Oregon, Tennessee, and selected counties in California, Colorado, and New York) about diseases that are caused by organisms commonly transmitted through food. FoodNet intensively seeks out every laboratory confirmed case of illness caused by 7 bacteria and 2 parasites in a catchment area that represents 15% of the US population (46 million Americans). It is designed to detect everyone in the 10 sites who went to their doctor's office, had a sample tested and was diagnosed with one of these infections.

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