CDC report outlines causes and outcomes of multi-state outbreaks

Recently published research shows that Salmonella caused the highest number of multi-state intestinal disease outbreaks in 2023.

The report from the Centers for Disease Control and Prevention found that the agency investigated 181 possible multi-state outbreaks and determined 84 of the incidents to actually be multi-state outbreaks. 

Investigators determined the cause of 50 of the outbreaks, for a 60 percent solve rate.

The 84 outbreaks investigated caused at least 3,153 illnesses, 942 hospitalizations and 10 deaths. The true number of sick people was likely much higher because some people do not seek medical attention and others are not specifically tested for foodborne pathogens. For example, the CDC estimates that for every confirmed patient in a Salmonella outbreak, there are 29 patients who go undetected.

Of the 50 solved outbreaks, 32 were linked to contaminated food and caused 1,219 illnesses, 421 hospitalizations, and 9 deaths. The remaining 18 solved multi-state outbreaks were linked to animal contact and caused 1,220 illnesses, and 290 hospitalizations. Backyard flocks of chickens were found to be the most frequent cause of outbreaks from animal contact.

“Among all illnesses related to solved foodborne outbreaks, 11 percent occurred in children under 5 and 30 percent occurred in adults over 65 years, age groups at higher risk for severe illness,” according to the report.

Fruits were identified as the source of the most solved foodborne outbreaks (5) during 2023. Vegetable row crops (4) and chicken (4) were also identified as common sources of foodborne outbreaks in 2023.

Backyard poultry was identified as the source of both the most solved outbreaks at 14 and the most outbreak-associated illnesses with 1,127 of any animal contact category in 2023.

As with findings of previous summaries, Salmonella caused the highest number of multi-state outbreaks with 54, as well as the most and illnesses with 2,848, making up 64 percent of the multi-state outbreaks investigated and 90 percent of the illnesses. 

Salmonella caused most of the solved multi-state foodborne outbreaks with 16 outbreaks or 50 percent, followed by Listeria with seven outbreaks at 22 percent, STEC with seven outbreaks at 22 percent, and Campylobacter with two outbreaks at 6 percent.

More multi-state outbreaks were investigated by CDC in 2023 than any year since 2016. The number of multi-state outbreaks investigated in 2023 increased from 2022 for all pathogens except Listeria, which caused the same number of outbreaks in 2022 and 2023.

A suspected source was identified in 56 percent of foodborne outbreaks and a confirmed source was identified for 44 percent. These solved multi-state foodborne outbreaks were associated with 1,219 illnesses, 421 hospitalizations, and nine deaths. Ill people in these outbreaks ranged in age from less than 1 to 100 years, with a median age of 47 years. When compared with Salmonella, STEC, and Campylobacter infections, a higher proportion of solved multi-state foodborne outbreaks of Listeria infections were in adults aged 65 and over with 61 percent, compared to 30 percent, 11 percent, and 33 percent, respectively).

In 2023, CDC issued outbreak notices for 11 investigations. The 11 investigations included eight linked to contaminated foods — seven with a confirmed source and one with a suspected source — and three linked to animal contact or pet food. Among the seven investigations with a confirmed food source, five resulted in food recalls, and one resulted in the food item not being sold temporarily. Among the three animal contact or pet food investigations, one resulted in a pet food recall. In total, the outbreak notices received more than 2 million page views, including a large Salmonella outbreak linked to fresh diced onions which received more than 1 million views.

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Source: https://www.foodsafetynews.com/2025/09/cdc-report-outlines-causes-and-outcomes-of-multi-state-outbreaks/