CDC - Surveillance study on the cause of reported foodborne Outbreaks

CDC issued a surveillance study on the cause of reported foodborne Outbreaks.

• During 2009–2015, FDOSS received reports of 5,760 outbreaks, resulting in 100,939 illnesses, 5,699 hospitalizations, and 145 deaths 
• Where a single agent was confirmed (in 2,953 outbreaks) with a single confirmed etiology, 

1. Norovirus was the most common cause of outbreaks (1,130 outbreaks [38%]) and outbreak-associated illnesses (27,623 illnesses [41%]). 
2. Salmonella was the second most common single confirmed etiology reported, with 896 outbreaks (30%) and 23,662 illnesses (35%)
3. Shiga toxin-producing Escherichia coli (STEC) (191 outbreaks [6%]), 
4. Campylobacter (155 [5%]), 
5. Clostridium perfringens (108 [4%]), 
6. Scombroid toxin (95 [3%]), 
7. Ciguatoxin (80 [3%]), 
8. Staphylococcus aureus (35 [1%]), 
9. Vibrio parahaemolyticus (35 [1%]), and 
10. Listeria monocytogenes (35 [1%]). 

• Listeria, Salmonella, and STEC were the most common causes of hospitalizations (82%) and deaths (82%) reported among persons in outbreaks with a single confirmed etiology.
• Salmonella and STEC were two of the most common causes of large outbreaks.
• Restaurants accounted for the largest percentage followed by Catering, Private Home, and then Institutional.
• The food categories responsible for the most outbreak-associated illnesses were chicken (3,114 illnesses [12%]), pork (2,670 [10%]), and seeded vegetables (2,572 [10%]).
• The pathogen-food category pairs that caused the most outbreak-associated illnesses were Salmonella in eggs (2,422 illnesses), Salmonella in seeded vegetables (2,203), and Salmonella in chicken (1,941

Limitation of analysis:

1. "Because CDC’s foodborne outbreak surveillance is dynamic and agencies can submit, update, or delete reports at any time, the results of this analysis might differ slightly from previous or future reports". 
2. "Not all outbreaks are identified and the majority of foodborne illnesses occur outside the context of a recognized outbreak. The degree to which the food vehicles, etiologies, and locations implicated in outbreaks represent the vehicles, etiologies, and locations of sporadic foodborne illness is unknown." 
3. "Some outbreaks have an unknown food vehicle, an unknown etiology, or both, and analyses and conclusions drawn from outbreaks with an identified food vehicle and confirmed etiology might not be representative of all outbreaks." 
4. "Pathogens that are not known to cause illness sometimes are reported as a confirmed or suspected etiology."

https://www.cdc.gov/mmwr/volumes/67/ss/ss6710a1.htm?s_cid=ss6710a1_e
Surveillance for Foodborne Disease Outbreaks — United States, 2009–2015
Surveillance Summaries / July 27, 2018 / 67(10);1–11

CDC MMWR - Waterborne Disease Outbreaks from Drinking Water - 2013 to 2014

As an important raw material for most food operations, water must be evaluated as part of the hazard analysis. The source of the water as well as how that water is stored and used must be considered. In CDC's report, disease outbreaks associated with drinking water (period 2013-2014) are reviewed. By their definition, "for an event to be defined as a waterborne disease outbreak, two or more cases must be linked epidemiologically by time, location of water exposure, and illness characteristics; and the epidemiologic evidence must implicate water exposure as the probable source of illness."

A summary of key findings:

• "Legionella was implicated in 24 (57%) outbreaks, 130 (13%) cases, 109 (88%) hospitalizations, and all 13 deaths (Table 1). Eight outbreaks caused by two parasites resulted in 289 (29%) cases, among which 279 (97%) were caused by Cryptosporidium, and 10 (3%) were caused by Giardia duodenalis. Chemicals or toxins were implicated in four outbreaks involving 499 cases, with 13 hospitalizations, including the first reported outbreaks (two outbreaks) associated with algal toxins in drinking water."
• "Thirty-five (83%) outbreaks were associated with public (i.e., regulated), community or noncommunity water systems,¶ and three (7%) were associated with unregulated, individual systems. Fourteen outbreaks occurred in drinking water systems with groundwater sources and an additional 14 occurred in drinking water systems with surface water sources. The most commonly cited deficiency, which led to 24** (57%) of the 42 drinking water–associated outbreaks, was the presence of Legionella in drinking water systems"
• "All of the outbreak-associated deaths reported during this surveillance period as well as all of the outbreaks reported in hospital/health care settings or long-term care facilities, were caused by Legionella. A review of 27 Legionnaires’ disease outbreak investigations in which CDC participated during 2000–2014 identified at least one water system maintenance deficiency in all 23 investigations for which this information was available, indicating that effective water management programs in buildings at increased risk for Legionella growth and transmission (e.g., those with more than 10 stories or that house "
• "Cryptosporidium was the second most common cause of both outbreaks and illnesses, demonstrating the continued threat from this chlorine-tolerant pathogen when drinking water supplies are contaminated."

Some background from one of the references (copied below) on Legionella in water systems.

• "Legionnaires’ disease is a lung infection that is fatal for about one in 10 persons who become infected. Legionella, the bacterium that causes Legionnaires’ disease, grows well in warm water, but can be killed by disinfectants, such as chlorine. Persons can get Legionnaires’ disease when they breathe in small droplets of water contaminated with Legionella."
• "Legionella grows best in building water systems that are not well maintained, especially where levels of chlorine or other disinfectants are low and water temperatures are optimal for its growth. Legionnaires’ disease outbreaks most often occur in hotels, long-term care facilities, and hospitals. The most common sources are potable water (e.g., drinkable water used for showering), cooling towers, hot tubs, and decorative fountains."

CDC MMWR
https://www.cdc.gov/mmwr/volumes/66/wr/mm6644a3.htm?s_cid=mm6644a3_e
Surveillance for Waterborne Disease Outbreaks Associated with Drinking Water — United States, 2013–2014
Weekly / November 10, 2017 / 66(44);1216–1221

CDC Study - Outbreaks Associated with Organic Foods

A study conducted by CDC evaluated the outbreaks associated with organic foods.  From the study: "We identified 18 outbreaks caused by organic foods from 1992 to 2014, resulting in 779 illnesses, 258 hospitalizations, and 3 deaths".  Salmonella and pathogenic E.coli were the leading causes.  There were a range of foods involved: "Eight of the outbreaks were attributed to produce items, four to unpasteurized dairy products, two to eggs, two to nut and seed products, and two to multiingredient foods."  

As stated in this study, it is hard to calculate risk of organic foods compared to conventional foods.  However, we can say that just because it is organic, it doesn't mean that you still don't need proper handling and preparation.

It is also important to point out that over the period of time covered in this study, the capabilities for identifying outbreaks and tracking to the source have improved greatly.  So looking at the number of outbreaks occurring from year to year can be misleading.

Journal of Food Protection, November 2016
http://www.ingentaconnect.com/content/iafp/jfp/2016/00000079/00000011/art00018
Foodborne Disease Outbreaks Associated with Organic Foods in the United States

CDC Report: Listeria Illnesses, Deaths, and Outbreaks — United States, 2009–2011

CDC just released a report detailing Listeria outbreaks in the United States, 2009-2011. In this time frame, ,1651 cases were reported nationally. 

In summary, Listeria monocytogenes is a foodborne pathogen that primarily impacts those in high risk groups – elderly, immunocompromised, and pregnant women. Listeria infection in these individuals leads to bacteremia (bacterial blood infection), meningitis, and death (mortality rate of 21%).

Soft cheeses and cheeses made from unpasteurized milk are the primary vehicles, although there have been cases related to produce (cut celery and cantaloupe). So for high risk groups, individuals in these high risk groups may want to forgo the soft cheeses, cheeses made from unpasteurized milk, and unpasteurized milk.

I think it is important to note what is not on list of responsible food items in this reporting period – deli meats. The meat industry has done a good job in reducing the risk associated with those ready-to-eat meat items. But work needs to continue with all refrigerated RTE items that can support the growth of Listeria. Recently, an interagency report on the risk of Listeria in Retail Delicatessens (http://pennstatefoodsafety.blogspot.com/2013/05/risk-assessment-of-listeria-in-retail.html) highlighted the practices retail stores can take to reduce the risk of Listeria contamination.


CDC MMWR Repot  http://www.cdc.gov/mmwr/preview/mmwrhtml/mm62e0604a1.htm?s_cid=mm62e0604a1_w

Vital Signs: Listeria Illnesses, Deaths, and Outbreaks — United States, 2009–2011

Early Release
June 4, 2013 / 62(Early Release);1-5

Abstract

Background: Older adults, pregnant women, and persons with immunocompromising conditions are at higher risk than others for invasive Listeria monocytogenes infection (listeriosis), a rare and preventable foodborne illness that can cause bacteremia, meningitis, fetal loss, and death.

Methods: This report summarizes data on 2009–2011 listeriosis cases and outbreaks reported to U.S. surveillance systems. The Listeria Initiative and PulseNet conduct nationwide surveillance to rapidly detect and respond to outbreaks, the Foodborne Diseases Active Surveillance Network (FoodNet) conducts active, sentinel population–based surveillance to track incidence trends, and the Foodborne Disease Outbreak Surveillance System (FDOSS) receives reports of investigated outbreaks to track foods and settings associated with outbreaks.

Results: Nationwide, 1,651 cases of listeriosis occurring during 2009–2011 were reported. The case-fatality rate was 21%. Most cases occurred among adults aged ≥65 years (950 [58%]), and 14% (227) were pregnancy-associated. At least 74% of nonpregnant patients aged <65 years had an immunocompromising condition, most commonly immunosuppressive therapy or malignancy. The average annual incidence was 0.29 cases per 100,000 population. Compared with the overall population, incidence was markedly higher among adults aged ≥65 years (1.3; relative rate [RR]: 4.4) and pregnant women (3.0; RR: 10.1). Twelve reported outbreaks affected 224 patients in 38 states. Five outbreak investigations implicated soft cheeses made from pasteurized milk that were likely contaminated during cheese-making (four implicated Mexican-style cheese, and one implicated two other types of cheese). Two outbreaks were linked to raw produce.
Conclusions: Almost all listeriosis occurs in persons in higher-risk groups. Soft cheeses were prominent vehicles, but other foods also caused recent outbreaks. Prevention targeting higher-risk groups and control of Listeria monocytogenes contamination in foods implicated by outbreak investigations will have the greatest impact on reducing the burden of listeriosis.

Implications for Public Health Practice: Careful attention to food safety is especially important to protect vulnerable populations. Surveillance for foodborne infections like listeriosis identifies food safety gaps that can be addressed by industry, regulatory authorities, food preparers, and consumers.