12 Charts Explore America's Salmonella Problem—and Steps to Solve It

Stronger rules for poultry would spur action on farms

Data Visualization December 10, 2021 Read time:

Projects: Safe Food

A million Americans a year are sickened by foodborne Salmonella, and current food safety policies and regulations don’t do enough to reduce these illnesses, particularly those from poultry products. Americans are falling ill from Salmonella-contaminated food at rates virtually unchanged from those in 2000, and chicken is still frequently linked to outbreaks.¹

Federal data from the past two decades underscores the lack of meaningful progress in reducing these infections. They also suggest ways that food regulators and producers can better protect consumers by targeting Salmonella contamination and serotypes, or varieties, in the poultry supply chain earlier and more precisely. The Food Safety and Inspection Service (FSIS)—the U.S. Department of Agriculture agency overseeing meat and poultry safety—should update its policies and regulations to apply these lessons and lower the rates of foodborne disease.

In a promising move, USDA officials announced plans in Oct. 2021 to pilot and study innovative strategies that could help decrease poultry-related Salmonella illnesses. “Time has shown that our current policies are not moving us closer to our public health goal,” said Sandra Eskin, who as deputy under secretary for food safety is leading the initiative. “It’s time to rethink our approach.”

Goal Set, Not Met

Foodborne Salmonella causes an estimated 1 million illnesses and 19,000 hospitalizations each year.² In 2010, the federal government set a goal to cut the nation’s incidence rate by 24% over a decade to 11.4 cases per 100,000 people—which the nation’s food producers and regulators are not yet close to meeting.³

Note: Foodborne Diseases Active Surveillance Network data includes infections detected by laboratory tests that involve culturing, or growing, bacteria and culture-independent diagnostic methods.

Source: Centers for Disease Control and Prevention, Foodborne Diseases Active Surveillance Network (FoodNet)

© 2021 The Pew Charitable Trusts

Chicken Contamination Shrank by Some Measures

Many varieties of Salmonella persistently challenge chicken and turkey producers because the organisms can thrive in a bird’s digestive tract, so effective control of these pathogens requires multiple interventions. Under FSIS policies, a poultry processor’s efforts to curb contamination are judged by the percentage of product samples that contain any amount or serotype of Salmonella. Against this broad presence-or-absence yardstick, contamination rates have decreased over the past two decades for some types of chicken products. Contamination rates have also declined in chicken breast samples taken from selected retail stores as part of the National Antimicrobial Resistance Monitoring System for Enteric Bacteria (NARMS).⁴

Note: The Food Safety and Inspection Service started sampling and testing chicken parts for *Salmonella* in 2015 as performance standards for this product category were implemented. The agency did not test any ground chicken products in 2014, so no data is available.

Sources: U.S. Department of Agriculture Food Safety and Inspection Service, National Antimicrobial Resistance Monitoring System

© 2021 The Pew Charitable Trusts

. . . But Salmonella Outbreaks Linked to Chicken Have Increased

Despite fewer product samples testing positive for the pathogen, the number of outbreaks associated with chicken products rose from 2000 to 2018.⁵ Federal estimates for 2019—the latest available—ranked chicken as the food commodity most linked to Salmonella infections, causing 1 in 6 cases. ⁶ These statistics indicate that FSIS’s current rules don’t adequately reflect and reduce the factors driving public health risks.

Source: Centers for Disease Control and Prevention, National Outbreak Reporting System

© 2021 The Pew Charitable Trusts

“Time has shown that our current policies are not moving us closer to our public health goal. It’s time to rethink our approach.”
Sandra Eskin, Deputy Under Secretary for Food Safety U.S. Department of Agriculture

Stronger Rules Needed to Curb Harmful Serotypes

Today’s FSIS regulations don’t effectively incentivize poultry producers to target the Salmonella serotypes of greatest public health importance because reducing the prevalence of any variety—even those that pose little or no risk to people—can count as success. Serotypes of long-standing concern, such as Enteritidis, have not significantly decreased as sources of human infections, and new threats have emerged unchecked. For example, current FSIS rules and producers’ food safety plans failed to contain the spread of Infantis, which contaminated dozens of chicken processing facilities and caused a 32-state outbreak of multidrug-resistant infections in 2019.⁷

Sources: U.S. Department of Agriculture Food Safety and Inspection Service, National Antimicrobial Resistance Monitoring System

© 2021 The Pew Charitable Trusts

Targeted, On-Farm Strategies Work

Infections from certain Salmonella serotypes have declined significantly, most likely due to food safety interventions before animals reach the slaughterhouse door. During the past two decades, poultry operations began vaccinating their flocks against Typhimurium, and product contamination and human illnesses from the serotype have steadily dropped during this period. The vaccine also proved beneficial in fighting serotype Heidelberg.⁸

Conclusion

Current poultry policies and regulations treat all Salmonella serotypes and strains as if they pose equal risks to people, despite science showing this is not the case.⁹ Food safety interventions on farms, such as vaccines targeting harmful serotypes, have likely contributed to meaningful reductions in product contamination and human illness. FSIS should revise its rules to focus more intensively on the serotypes causing more frequent or severe infections, and implement other policies to prompt poultry operations to adopt on-farm practices that control these hazards. Such a risk-based approach would help prevent illnesses and outbreaks linked to poultry products and drive down the nation’s unacceptably high number of Salmonella illnesses.

Methodology

The table below summarizes the sources of data obtained for this analysis from 2000 to 2019 as well as the calculations. The data was obtained from federal government websites, via email correspondence with agencies, and through a Freedom of Information Act (FOIA) request.

Type of data	Source	Comment
Total human incidence of Salmonella sp. (cases per 100,000)	FoodNet Fast https://wwwn.cdc.gov/foodnetfast/	Results include results from culture and culture independent diagnostic tests (CIDTs).
Serotype-specific human incidence (cases per 100,000)	Provided to Pew by CDC/FoodNet via email
Salmonella sp. percentage positive for chicken (carcass, ground, and parts)	USDA/FSIS From 2015 to 2020: https://www.fsis.usda.gov/science-data/data-sets-visualizations/microbiology/microbiological-testing-program-rte-meat-and-7 From 2000 to 2014: https://www.fsis.usda.gov/sites/default/files/media_file/2020-10/Salmonella-Serotype-Annual-2014.pdf and https://www.fsis.usda.gov/sites/default/files/media_file/2021-02/Progress-Report-Salmonella-Campylobacter-CY2014.pdf	From 2015 to 2020: The total number of samples tested and number of positives for each quarter for all establishment sizes was obtained, then the percentage positive per year for each product category (carcass, parts, and ground/comminuted chicken) calculated. From 2000 to 2014: The percentage positive for each year for all establishments was extracted from the reports. For ground chicken, no samples were tested in 2014 (we sent an email to the agency, which confirmed this). No data for parts was available; FSIS only started testing that commodity in 2015.
Salmonella sp. percentage positive for chicken breast at retail	Provided to Pew by FDA/NARMS staff via email
Number of Salmonella outbreaks and illnesses	National Outbreak Reporting System (NORS) Dashboard https://wwwn.cdc.gov/norsdashboard/	Data was extracted from the dashboard using the following parameters: food as primary mode; 2000 to 2018; all states; all outbreaks; Salmonella (etiology); all settings; all foods/ingredients; all water exposures; all water types. Then, only data having “chicken” identified under the “IFSAC category” column was included in the analysis.
Percentage of specific Salmonella sp. serotypes isolated from chicken (carcass, ground, and parts)	From 2015 to 2020: Data.gov for raw chicken carcass, raw chicken parts, and raw ground/comminuted chicken https://catalog.data.gov/dataset/fsis-raw-chicken-parts-sampling-data From 2000 to 2014: https://www.fsis.usda.gov/sites/default/files/media_file/2020-10/Salmonella-Serotype-Annual-2014.pdf and https://www.fsis.usda.gov/sites/default/files/media_file/2021-02/Progress-Report-Salmonella-Campylobacter-CY2014.pdf	From 2015 to 2020: The data included Salmonella testing results for the five years, negative and positive samples. For the positive samples, serotypes were identified and recorded. The percentage of serotype A for a particular year was calculated by dividing the number of Salmonella from serotype A by all Salmonella isolated in that year. From 2000 to 2014: The percentage of total positives was extracted from the two reports for ground/comminuted chicken and chicken carcasses. For ground chicken, no samples were tested in 2014 (we sent an email to the agency, which confirmed this). We used the data obtained from a FOIA request to fill a few gaps from the reports.
Percentage of specific Salmonella sp. serotypes isolated from chicken breast at retail and cecal samples	From 2015 to 2019, serotype data for the selected serotypes was provided to Pew by FDA/NARMS via email. From 2002 to 2014, the frequency by serotype and total Salmonella positive was extracted from several reports. https://www.fda.gov/media/97546/download	For 2015 to 2017, only frequencies were provided, so the percentage by serotype by year was calculated. From 2002 to 2014, the frequency by serotype and total Salmonella positive was extracted and the percentage by serotype calculated.

Limitations

No formal statistical analysis was conducted in this study to determine correlation and causation or whether the rate increases and decreases over time were statistically significant. More in-depth analysis is needed to derive such conclusions.

There were also a few limitations associated with the data analyzed. The data used to attribute Salmonella illnesses to specific foods (e.g., chicken) is derived from outbreaks. Despite the improvements in outbreak detection and investigation, those illnesses represent only a small fraction of total illnesses. To more accurately quantify the contribution of chicken to Salmonella infections, it is important to understand the sources of exposure and specific serotypes associated with sporadic cases (i.e., cases not considered part of an outbreak). Further, FSIS has made several changes in its sample collection and testing methods over the period analyzed.^10,11 Those changes were not taken into consideration in this study but could have resulted in an increase in the detection of Salmonella related to the use of improved methods and larger sample sizes. The datasets presented come from surveillance systems that have different goals and objectives, and data from these sources is not often presented side by side.

Regardless of these limitations, there is value in using these large datasets for exploratory analyses and early detection of patterns and trends that can be further explored with more robust data and analyses. Agencies should take advantage of these resources and, on an ongoing basis, evaluate and monitor for trends.

Endnotes

Centers for Disease Control and Prevention, Foodborne Diseases Active Surveillance Network (Foodnet), 1996-2019, accessed Sept. 22, 2021, https://wwwn.cdc.gov/foodnetfast/; Centers for Disease Control and Prevention, National Outbreak Reporting System (NORS), 1971-2018, accessed Sept. 22, 2021, last modified Dec. 7, 2018, https://wwwn.cdc.gov/norsdashboard/.
E. Scallan et al., “Foodborne Illness Acquired in the United States—Major Pathogens,” Emerging Infectious Diseases 17, no. 1 (2011): 7-15, https://dx.doi.org/10.3201/eid1701.p11101.
U.S. Department of Health & Human Services, “Healthy People 2020,” last modified Sept. 14, 2021, accessed Sept. 22, 2021, https://www.healthypeople.gov/2020/topics-objectives/topic/food-safety/objectives.
U.S. Food & Drug Administration, “National Antimicrobial Resistance Monitoring System: Integrated Reports and Summaries,” last modified Dec. 11, 2020, accessed Sept. 22, 2021, https://www.fda.gov/animal-veterinary/national-antimicrobial-resistance-monitoring-system/integrated-reportssummaries.
Centers for Disease Control and Prevention, National Outbreak Reporting System (NORS).
The Interagency Food Safety Analytics Collaboration (IFSAC), “Foodborne Illness Source Attribution Estimates for Salmonella, Escherichia Coli O157, Listeria Monocytogenes, and Campylobacter Using Multi-Year Outbreak Surveillance Data, United States” (2021), https://www.cdc.gov/foodsafety/ifsac/annual-reports.html.
Centers for Disease Control and Prevention, “Outbreak of Multidrug-Resistant Salmonella Infections Linked to Raw Chicken Products, Final Update,” last modified Feb. 21, 2019, accessed Sept. 22, 2021, https://www.cdc.gov/salmonella/infantis-10-18/index.html.
D. Tack et al., “Preliminary Incidence and Trends of Infections with Pathogens Transmitted Commonly Through Food—Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 2016–2019,” Morbidity and Mortality Weekly Report 69, no. 17 (2020): 509-14, https://www.cdc.gov/mmwr/volumes/69/wr/mm6917a1.htm?s_cid=mm6917a1_w.
A. Cohn et al., “Moving Past Species Classifications for Risk-Based Approaches to Food Safety: Salmonella as a Case Study,” Frontiers in Sustainable Food Systems 5 (2021), https://www.frontiersin.org/articles/10.3389/fsufs.2021.652132/full.
A. Beczkiewicz and B. Kowalcyk, “Risk Factors for Salmonella Contamination of Whole Chicken Carcasses Following Changes in U.S. Regulatory Oversight,” Journal of Food Protection (2021), https://pubmed.ncbi.nlm.nih.gov/34047797/.
M. Ollinger et al., “Food Safety Audits, Plant Characteristics, and Food Safety Technology Use in Meat and Poultry Plants” (U.S. Department of Agriculture: Economic Research Service, 2011).