About 800 foodborne illness outbreaks occur in the United States every year, sickening more than 15,000 people, with one of the most frequent causes of contamination coming from animal or environmental sources before arriving at the point of final preparation.
Data from a new study by the Centers for Disease Control and Prevention also shows food service workers as one of the main causes of outbreaks from 2014 through 2022.
In a new report, “Contributing Factors of Foodborne Illness Outbreaks — National Outbreak Reporting System, United States, 2014–2022” the CDC discusses key elements in the U.S. food system.
The report says 800 confirmed outbreak patients are hospitalized every year, with 20 deaths confirmed as being from foodborne outbreaks. The numbers are likely much higher as there are an estimated 29 patients for every confirmed patient in Salmonella outbreaks and an estimated 26 patients for every confirmed patient in E. coli outbreaks.
“A foodborne illness outbreak is defined as two or more cases of a similar illness associated with a common exposure (e.g., shared food, venue, or experience). Data collected from an outbreak investigation help the investigator identify contributing factors to the outbreak,” according to the report.
“Contributing factors are food preparation practices, behaviors, and environmental conditions that lead to pathogens getting into food, growing in food, or surviving in food and are grouped into three categories: contamination (when pathogens and other hazards get into food); proliferation (when pathogens that are already present in food grow); and survival (when pathogens survive a process intended to kill or reduce them).”
Information on outbreaks comes from the Foodborne Disease Outbreak Surveillance System (FDOSS) via the National Outbreak Reporting System (NORS), which captures data from foodborne enteric illness outbreak investigations in the United States. Epidemiology or communicable disease control and environmental health programs of state and local health departments collect and voluntarily report the data to NORS.
A total of 2,677 foodborne illness outbreaks reported during 2014–2022 with information on contributing factors were included in the analysis. Foodborne outbreak periods were categorized into three time frames: 2014–2016 (first), 2017–2019 (second), and 2020–2022 (third). A foodborne illness outbreak is defined as two or more cases of a similar illness associated with a common exposure, such as shared food, venue, or experience.
The study did not include data from all of the outbreaks from the covered time frames. Overall, there was a total of 6,618 foodborne illness outbreaks reported to NORS from 2014 through 2022. Outbreaks were excluded from analysis if a contributing factor was not reported (3,788) or if a pathogen was identified in more than one etiologic category (23). An additional 126 viral outbreaks were excluded because a contributing factor that was not biologically feasible was reported.
Four outbreaks were excluded from the study because the contributing factors for the outbreaks were not plausible. The final dataset consisted of 2,677 foodborne illness outbreaks.
“For outbreaks with a contamination contributing factor, the proportion of food contaminated by an animal or environmental source before arriving at the point of final preparation increased over the three time frames — 22.2 percent in the first, 27.7 percent in the second, and 32.3 in the third,” according to the report.
The proportion of outbreaks with contamination from an infectious food worker through barehand contact with food decreased from 20.5 percent in the first time frame to 8.9 during the third. The report authors speculated that the decrease was related to the Covid pandemic, which saw improved worker hygiene.
“For viral outbreaks, contamination from an infectious food worker through barehand contact with food was among the most common contributing factors during the first (47.1%) and second time frame (37.7%) and decreased to the third most common contributing factor during the third time frame (28.7%),” according to the report.
The report data showed that two common contributing factors to bacterial outbreaks are allowing foods to remain out of temperature control for a prolonged period and inadequate time and temperature control during cooking.
The researchers reported that popular trends among consumers have an impact on the number of foodborne illness outbreaks. For example, they wrote, that drinking unpasteurized milk and eating undercooked chicken livers likely influenced the pattern of outbreak contributing factors identified in the study.
The data showed that overall, food contaminated by an animal or environmental source before arriving at the point of final preparation increased from 22.2 percent in the first time frame to 32.3 percent in the third time frame.
“Certain foods contaminated pre- or post-harvest are intended to be consumed raw, such as leafy greens and fresh produce, and controls, such as sanitation controls at a processing facility, are required before these foods reach the retail establishment to mitigate contamination,” the report states.
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