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New CDC Data Provides Insight About Foodborne Illness

Department of Food Science > New CDC Data Provides Insight About Foodborne Illness

New CDC Data Provides Insight About Foodborne Illness Challenges and Interventions


Richard H. Linton

Professor of Food Safety at Purdue University

 

The most recent data from the Centers for Disease Control and Prevention (CDC), relative to foodborne disease outbreaks in the United States, was published this past summer in the Morbidity and Mortality Weekly Report (MMWR).  CDC still estimates a total of 76 million illnesses occur annually in the United States, which amounts to nearly 1 in every 4 people.  The most recent report provides information as to the causes of foodborne illness and types of foods implicated in foodborne illness incidents in the year 2007. 

 

Epidemiologic data was provided for 1,097 reported outbreaks.  These outbreaks resulted in 21,244 cases of foodborne illness and 18 deaths.  Among the 497 foodborne outbreaks where a laboratory-confirmed single causative agent could be identified, Norovirus and Salmonella spp. were the number 1 and number 2 reported agent, respectively.   Table 1 provides a summary of the top 10 bacterial associated foodborne illnesses, and the top 2 viral, parasitic, and chemical causes of foodborne illness.    It is interesting to note that Norovirus, Salmonella spp., and Clostridium perfringens accounted for 85% of 2007 reported U.S. foodborne illnesses.    

 

Table 1.  Agents involved in foodborne illness for the most commonly reported bacterial pathogens (10), viruses (2), parasite (2), and chemicals (2), based on 2007 CDC data.  

                                                                           Agent causing illness

Agent       Type

Total # Outbreaks

Total # Illnesses

% of Total  Illness

Norovirus

Virus

317

8,024

52

Salmonella

Bacteria

142

3,515

23

Clostridium perfringens

Bacteria

45

1,606

10

Escherichia coli, Shiga toxin-producing

Bacteria

42

603

4

Campylobacter

Bacteria

27

372

2

Shigella

Bacteria

11

355

2

Staphylococcus enterotoxin

Bacteria

21

286

2

Bacillus cereus

Bacteria

19

164

1

Ciguatoxin

Chemical

14

84

 

0

S

combroid toxin/Histamine

Chemical

20

74

0

Giardia

Parasite

2

51

0

Hepatitis A

Virus

4

28

0

Clostridium botulinum

Bacteria

4

16

0

Cryptosporidium

Parasite

3

14

0

Vibrio parahaemolyticus

Bacteria

1

5

0

Listeria

Bacteria

1

5

0

 

In 235 outbreaks, a single food commodity was identified as the cause of illness.  Poultry, beef, and leafy vegetables were most often the cause of illness. The commodities most commonly implicated in outbreaks were finfish, poultry, and beef.   The commodities associated with the most illnesses were poultry, beef and leafy vegetables (refer to table 2).

 

Table 2.  Food commodities involved in foodborne illness for most commonly reported commodity groups based on 2007 CDC data.  

 

Commodities Implicated in Foodborne Illness

Total # Outbreaks

Total # Illnesses

Poultry

40

691

Beef

33

667

Leafy Greens

NA*

590

Finfish

41

NA*

                                                                                   *NA – data not available

 

Of most interest is the “combined pathogen-commodity pairs” that were responsible for the most outbreak-related illnesses.  These wer

e:

1.  

    Norovirus in leafy vegetables (315 illnesses),

2.      E. coli O157:H7 in beef (298 illnesses) and,

3.      Clostridium perfringens in poultry (281 illnesses).¶

This information is useful for us to set priorities of developing risk-based interventions, from the farm to the fork.  Interventions for each of these pathogen-commodity pairs are described below.

 

Interventions for Norovirus in leafy vegetables

Noroviruses are transmitted directly from person to person and indirectly via contaminated water and food. They are highly contagious viruses, with as few as ten virus particles being able to cause infection. Transmission occurs through ingesting contaminated food and water and by person-to-person spread. Transmission is predominantly from the fecal-to-oral route.  The virus can also be aerosolized when those stricken with the illness vomit, and, infection can follow eating food near an episode of vomiting, even if cleaned up. The viruses continue to be shed after symptoms have subsided and shedding can still be detected many weeks after infection.  

 

Salad ingredients, like leafy greens, are often implicated in norovirus outbreaks.  Frequent and proper handwashing (at the farm, during distribution, and in retail/foodservice settings) is the most effective method to reduce the spread of norovirus.  Sanitizing of surfaces where the norovirus may be present is recommended.  Alcohol rubs are not very effective at controlling norovirus.  CDC has prepared a technical fact sheet (http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirus-factsheet.htm) that describes the best control measures for norovirus.

 

Interventions for E. coli O157:H7 in beef

Escherichia coli O157:H7 is an enterohemorrhagic strain of the bacterium.  Infection often leads to hemorrhagic diarrhea, and occasionally to kidney failure, especially in young children and elderly people. Transmission is via the fecal-to-oral route, and most illness has been associated with eating undercooked, contaminated ground beef, swimming in or drinking contaminated water, and eating contaminated raw vegetables.

 

E. coli O157:H7 is found on cattle farms and can live in the intestines of healthy cattle.  Beef processing is a common point of contamination.  During the slaughtering process, the contents of intestines can come into contact with the meat.  Ground beef is much more likely to be a source of infection compared to a steak due to the increased surface area and routes of contamination that occur in the grinding process.  Accordingly, most of the effective measures to reduce E. coli O157:H7 can occur at the slaughtering facility that have included careful removal and cleaning of the intestines, steam/vacuum treatment, and organic acid sprays.  A detailed article “Guidance for Minimizing the Risk of Escherichia coli O157:H7 and Salmonella in Beef Slaughter Operations” (http://haccpalliance.org/alliance/BeefSlauterGuide.pdf) has identified some of these measures.

 

Within a retail/foodservice setting, cross-contamination control measures and good handwashing techniques are keys to preventing transmission of the bacteria.  Cooking ground beef to at least 155oF (68.5oC) for at least 15 seconds is the most effective measure to eliminate the organism. 

 

Interventions for Clostridium perfringens in poultry

C. perfringens is a spore-forming bacterium.  The bacterial spores convert to vegetative cells in the digestive tract of people and produce a toxin that can cause human illness.  The organism is widely distributed in the environment and frequently occurs in the intestines of humans and many domestic and feral animals. Spores of the organism persist in soil, sediments, and areas subject to human or animal fecal pollution.  C. perfringens poisoning is characterized by intense abdominal cramps and diarrhea which begin 8-22 hours after consumption of foods.    

Temperature abuse, including improper cooling, hot holding, and storage conditions have most commonly been associated with foods believed to be responsible for causing illness, whether these foods are prepared at foodservice, retail food establishments, institutions, or at the home.  An extensive risk assessment was completed in 2005 for C. perfringens in RTE and partially cooked meat and poultry products.  An executive summary is available at http://www.fsis.usda.gov/PDF/CPerfringens_Risk_Assess_ExecSumm_Sep2005.pdf.

 

Within the retail and foodservice setting, control of time and temperature is the most important mechanism for control of the C. perfringens organism, in particularly, for hot/cold holding and for cooling of PHF (TCS ) foods.   For food product holding, cold foods should be kept at 41oF (5oC) or below and hot foods kept at 135oF (57oC) or above.  Effective cooling is perhaps the most critical intervention.  PHF (TCS) foods should be cooled from 135 - 70oF (57 - 21oC) in less than 2 hours and from 135 - 41oF (57 - 5oC) in less than 6 hours.  

 

CDC data are an excellent source of information about the causes of foodborne illness and the types of foods implicated in these outbreaks.  This information can be valuable to all segments of the food industry when it comes to setting priorities and developing risk-based interventions from the farm to the fork.  By implementing these interventions on the farm, in processing plants, during transportation, and at retail food establishments, we will enhance the safety of our nation’s food supply.