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Questions and Answers, Surveillance for Foodborne Disease Outbreaks, 2011 and 2012

In May, 2014 CDC published two annual reports of foodborne disease outbreaks reported in calendar years 2011 and 2012 and updated its Foodborne Outbreak Online Database (FOOD) through 2012. Information on this page provides important background and summaries of both reports.

  • Full reports can be found on the Food Safety FDOSS Annual Summaries of Foodborne Outbreaks web page. 
  • A special CDC feature, New Data on Foodborne Disease Outbreaks, can be found here (will provide link to feature).

Background

Graph: Foodborne Disease Outbreaks, 2008. Source: Foodborne Disease Outbreak Surveillance System. 2008 was the most recent year for which outbreak data are finalized. Outbreaks reported: 1,034; Cases of illness: 23,152; Hospitalizations: 1,276; Deaths: 22.

These new outbreak reports for the years 2011 and 2012 are similar to previous summaries of outbreaks during 2006-2010 posted on the Food Safety FDOSS Annual Summaries of Foodborne Outbreaks web page.

  • CDC also maintains a web-based platform for searching CDC's Foodborne Disease Outbreak Surveillance System database called the Foodborne Outbreak Online Database (FOOD) that has been updated with information through 2012.
  • Summaries of outbreak investigations that state and local health departments report to CDC provide important snapshots of the human health impact of foodborne outbreaks and the pathogens (germs), foods, settings, and contributing factors (for example, food not kept at the right temperature) involved in these outbreaks.
  • It is important to note that we cannot directly compare the results in the 2011 and 2012 reports to prior years because of changes made to the foodborne disease outbreak surveillance system in 2009 and the use of a new food categorization scheme in 2011.

 

Fast Facts

Foodborne disease outbreaks, 2011-2012

Graph: Foodborne Disease Outbreaks, 2008. Source: Foodborne Disease Outbreak Surveillance System. 2008 was the most recent year for which outbreak data are finalized. Outbreaks reported: 1,034; Cases of illness: 23,152; Hospitalizations: 1,276; Deaths: 22.

During January 1, 2011 through December 31, 2012, public health departments reported 1,632 foodborne disease outbreaks; these outbreaks resulted in 29,112 illnesses, 1,750 hospitalizations, and 68 deaths.

Outbreaks and Pathogens, 2011-2012

  • 793 outbreaks were caused by a single, confirmed pathogen (germ)
  • The most common causes of reported outbreaks
    • Norovirus caused 41%
    • Salmonella caused 25%

Outbreak-related illnesses, 2011-2012

  • 18,880 outbreak-related illnesses were caused by a single, confirmed pathogen (germ) and 1,501 (8%) resulted in hospitalization
  • The most common causes of outbreak-related illnesses
    • Norovirus caused 46%
    • Salmonella caused 34%

 

Key Data from 2011 and 2012 Reports

What are the main findings from each report?

2011

  • 801 foodborne disease outbreaks reported, resulting in
    • 14,140 illnesses
    • 956 hospitalizations
    • 45 deaths
    • 27 food recalls

2012

  • 831 foodborne disease outbreaks reported, resulting in
    • 14,972 illnesses
    • 794 hospitalizations
    • 23 deaths
    • 20 food recalls

What pathogens (germs) caused the most outbreaks?

2011

  • 370 outbreaks were caused by a single, confirmed pathogen (germ). Most commonly reported pathogens
    • Norovirus caused 39% of outbreaks
    • Salmonella caused 29% of outbreaks

2012

  • 423 outbreaks were caused by a single, confirmed pathogen (germ). Most commonly reported pathogens
    • Norovirus caused 41% of outbreaks
    • Salmonella caused 25% of outbreaks

What pathogens (germs) caused the most outbreak-related illnesses?

2011

  • 8,561 outbreak-related illnesses were caused by a single, confirmed pathogen (germ) and 800 (9%) illnesses resulted in hospitalization
  • The most common pathogens (germs) resulting in outbreak-related illnesses:
    • Norovirus caused 46%
    • Salmonella caused 35%

2012

  • 10,319 outbreak-related illnesses were caused by a single, confirmed pathogen (germ) and 701 (7%) illnesses resulted in hospitalization
  • The most common pathogens (germs) resulting in outbreak-related illnesses:
    • Norovirus caused 45%
    • Salmonella caused 33%

What pathogen-food category pairs (germs and foods) were responsible for the most outbreaks and outbreak-related illnesses, hospitalizations, and deaths?

2011

The pathogen-food category pairs (germs and foods) responsible for the most outbreaks and outbreak-related illnesses, hospitalizations, and deaths were

  • Outbreaks
    • Campylobacter in unpasteurized dairy (15 outbreaks)
    • Ciguatoxin in fish (13 outbreaks)
    • Norovirus in fruits (11 outbreaks)
  • Illnesses
    • Salmonella in chicken (545 illnesses)
    • Norovirus in fruits (444 illnesses)
    • Salmonella in pork (227 illnesses)
  • Hospitalizations
    • Listeria in fruits (143 hospitalizations)
    • Salmonella in turkey (58 hospitalizations)
    • Shiga toxin-producing Escherichia coli in vegetable row crops (44 hospitalizations)
  • Deaths
    • Listeria in fruits (33 deaths)
    • Listeria in dairy (2 deaths)
    • Shiga toxin-producing Escherichia coli in fruits (2 deaths)

2012

The pathogen-food category pairs (germs and foods) responsible for the most outbreak-related illnesses, hospitalizations, and deaths were

  • Outbreaks
    • Scombroid toxin (histamine fish poisoning) in fish (17 outbreaks)
    • Campylobacter in unpasteurized dairy (10 outbreaks)
    • Vibrio parahaemolyticus in mollusks (10 outbreaks)
  • Illnesses
    • Salmonella in fruits (446 illnesses)
    • Salmonella in fish (425 illnesses)
    • Salmonella in chicken (345 illnesses)
  • Hospitalizations
    • Salmonella in chicken (109 hospitalizations)
    • Salmonella in fruits (55 hospitalizations)
    • Salmonella in fish (55 hospitalizations)
  • Deaths
    • Listeria in dairy (5 deaths)
    • Campylobacter in chicken (4 deaths)

Where were most foods that caused outbreaks prepared?

2011

  • 59% in a restaurant
  • 14% at home
  • 13% by a caterer or at a banquet facility

2012

  • 60% in a restaurant
  • 14% by a caterer or at a banquet facility
  • 13% at home

How many multistate outbreaks were reported?

Nineteen multistate outbreaks were reported during 2011.

  • Twelve were caused by Salmonella
  • Seven by Shiga toxin-producing E. coli
  • Two by Listeria
  • One by Vibrio cholerae

Twenty-four multistate outbreaks were reported during 2012.

  • Fifteen were caused by Salmonella
  • Five by Shiga toxin-producing E. coli
  • Two by Listeria
  • One by Campylobacter
  • One by Vibrio parahaemolyticus

For more information about selected multistate foodborne disease outbreaks, please visit the Food Safety Foodborne Outbreaks List of Selected Multistate Foodborne Outbreak Investigations web page.

 

General Questions about the Reports

What factors influence outbreak investigation and reporting by state, local, and territorial public health agencies?

Outbreak detection, investigation, and reporting are influenced by many factors such as

  • Available resources (time, staff, and laboratory capacity)
  • Health department priorities
  • Outbreak characteristics (size, severity)

Why do we use outbreak information to prevent foodborne illnesses? 

When illnesses occur outside an outbreak setting, it is usually impossible to know what food or other exposure caused them. Therefore, although only a small proportion of illnesses occur as part of recognized and reported outbreaks, outbreak investigations provide some of the best data about the sources of foodborne illnesses.

How can this information be used to prevent foodborne illnesses?

Examining outbreak data can offer insights into the pathogens agents and foods causing foodborne illnesses, and into the factors that contribute to their occurrence. Public health officials use this information for foodborne illness prevention, education, and policy.

Why is the food unknown for so many reported outbreaks? 

It is not always possible to determine what food is responsible for an outbreak. There are good reasons why excellent investigations sometimes do not identify the food source. For example, sometimes many of the same foods were eaten by most of the people who became sick, sometimes the number of people ill is very small, or sometimes the outbreak is identified after people’s memories have faded. We can learn a lot even without knowing the responsible food. For example, information about the pathogen, the setting (e.g., restaurant, home, school), the number ill, and whether someone died is useful in designing prevention measures.

CDC encourages states to report all foodborne outbreak investigations, even if the food is not determined. Even well-conducted investigations may be unable to identify the food that caused the outbreak.

Why is the etiology (cause) unknown for so many reported outbreaks?

Infections caused by bacteria, chemical agents and toxins, parasites, and viruses are often diagnosed using specific laboratory tests that can identify the pathogen.

Too often, outbreaks are identified after the optimal time to obtain specimens from ill people and so laboratory tests are negative; sometimes health departments are unable to obtain specimens for laboratory analysis. In outbreaks in which timely specimens were obtained and a pathogen is not identified by the usual tests done by clinical laboratories, the cause may be a pathogen that is not identified by tests done in the clinical laboratory. In these outbreaks, specimens should be sent to the state public health laboratory so that additional tests can be done there or at CDC.

CDC encourages states to report all foodborne disease outbreak investigations, even if the etiology is not determined. Even well-conducted investigations may not be able to identify the etiology or cause of the outbreak.

Can data reported in 2011 and 2012 be compared with previous years?

No. Because of changes made to the foodborne disease outbreak surveillance system in 2009 and the use of a new food categorization scheme in 2011, it is difficult to make comparisons with previous years.

Where can I go for more information on foodborne disease outbreaks?

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