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Outbreaks

Multiyear Listeria Outbreak Attributed to Peaches, Plums, &Nectarines

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Whole peaches, plums, and nectarines (i.e. stone fruit) have been implicated in a multistate outbreak of Listeria monocytogenes infections. Initially, an epidemiological investigation indicated
people in this outbreak were 18 times more likely to eat peaches, plums, or nectarines. Subsequent sampling and testing of 2lb bagged peaches from the supplier were found positive by FDA and linked with whole genome sequencing to the outbreak strain. Further analysis indicates that this outbreak has led to one death and eleven illnesses occurring as far back as August 2018.


This is not the first outbreak associated with stone fruit. An outbreak involving Salmonella Enteritidis contaminated peaches occurred in 2020 causing 101 reports of illness. In a 2014 outbreak, the first cases of listeriosis involving contaminated stone fruit (i.e. whole peaches, nectarines, plums, and pluots) were reported. Pathogens generally persist on the contaminated fruit surface (i.e. skin) and can cause illness if not properly sanitized before consumption.

An investigation report for the 2020 outbreak published by FDA examined the potential sources and routes of Salmonella product contamination from associated peach orchards and packing lines. Environmental samples were collected from the packing houses, product samples (peaches) from the packing houses and orchards, and peach tree leaves from the orchards during the investigations. All tested negative for presence of the outbreak strain. This may have been due to subsequent cleaning/sanitization and review/update of food safety programs that occurred during the product recall. However, multiple Salmonella isolates from product and leaf sampling genetically resembled previous chicken and cattle isolates, not associated with any known foodborne illnesses. FDA hypothesized that the adjacent animal operations (both poultry and cattle) were a likely contributing factor to the Salmonella Enteritidis outbreak – with fugitive dust as one possible route of product contamination.

Similar to Salmonella, L. monocytogenes is ubiquitous in nature. It can spread from the growing
environment to harvesting and packing equipment, establishing itself in the processing environment if poor sanitation practices are used. A 2014 outbreak involving L. monocytogenes contaminated whole apples found numerous locations in a processing facility positive for the pathogen where environmental surfaces came into contact with product.


Whole fruits, such as peaches, are considered a raw agricultural commodity and need to comply with regulations set forth in the Produce Safety Rule for the safe growing, harvesting, packing, and holding of fruits and vegetables grown for human consumption. Guidance to meet these requirements is available from FDA.

A Look Back at the U.S. Foodborne Outbreaks Occurring in 2023

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This article takes a look back at the foodborne outbreaks that occurred in 2023. Currently, 27 outbreaks have occurred involving Shiga toxin-producing E. coli, Salmonella, Listeria monocytogenes, Hepatitis A, Cyclospora, Cryptosporidium, natural toxins, and lead. This resulted in 1,076 reports of illness from the consumption of 14 known product types and 11 unknown product types. According to public health officials, these numbers are severely underreported. Many illnesses go unrecognized as being linked to a contaminated food. The table below provides a brief overview of the outbreaks reported by FDA, USDA FSIS, and CDC. Highlights are also provided for outbreaks having known product sources.

Foodborne Outbreaks Occurring in 2023

MonthProductPathogenIllness
February Leafy Greens L. monocytogenes19
March Frozen Strawberries Hepatitis A Virus 10
March Not Identified Salmonella Hartford 54
March Raw Flour Salmonella Infantis 14
April Morel Mushroom Natural Toxin 51
May Broccoli Cyclospora cayetanensis 20
May Raw Cookie Dough Salmonella Enteritidis 26
May Ground Beef Salmonella Typhimurium 26
June Pico de Gallo Salmonella Paratyphi B 37
June Not Identified Cyclospora cayetanensis 72
July Not Identified Cyclospora cayetanensis 140
July Not Identified E. coli O157:H7 12
July Not Identified E. coli O26 13
July Not Identified Cyclospora cayetanensis 59
July Ground Beef Salmonella Saintpaul 18
August Ice Cream L. monocytogenes 2
August Not Identified Cryptosporidium 11
August Ground Beef E. coli O157:H7 Not Reported
September Watermelon and Cantaloupe Salmonella Newport 11
October Onions Salmonella Thompson 80
November Not Identified E. coli O121:H19 37
November Apple Cinnamon Puree Elevated Lead Levels 65
November Not Identified E. coli O103 12
November Peaches, Plums, Nectarines L. monocytogenes 11
November Cantaloupe Salmonella Sundsvall & Oranienburg 230
November Not Identified Salmonella Newport 43
December Not Identified L. monocytogenes 3

February – Leafy greens were epidemiologically linked to nineteen illnesses involving L. monocytogenes occurring across 16 states. However, there was not enough data to identify a specific type or producer of the leafy greens.

March – Frozen organic strawberries sourced from farms located in Baja California, Mexico were linked to ten illnesses from hepatitis A virus. This outbreak strain was genetically identical to a previously isolated strain from fresh organic strawberries grown in Baja California, Mexico implicated in an outbreak in 2022.

March – Raw flour contaminated with Salmonella Infantis was linked to an outbreak that caused fourteen illnesses. Seven of the reported ill said they had consumed raw dough or batter prior to symptom onset.
April – Morel mushrooms served raw or lightly cooked at a sushi restaurant in Montana caused fifty one illnesses and two deaths. Left over mushrooms tested were found to be true morels and not false morels that contain the toxin gyromitrin. However, documented cases of similar illness have been reported due to low levels of naturally occurring heat-labile hydrazinic toxins found in the raw morels.
May – Broccoli caused an outbreak resulting in 20 illnesses from Cyclospora cayetanensis, however, likely
due to the short product shelf life, an advisory was never issued.
May – Raw cookie dough sold at a national retailer of take and bake pizzas was linked to an outbreak that caused twenty six illnesses resulting from Salmonella Enteritidis. Fifteen of the ill reported eating raw cookie dough from the retailer a week prior to when they got sick.
May – Ground beef was linked to an outbreak causing twenty six illnesses from Salmonella Typhimurium. Some of the ill people reported eating undercooked ground beef.
June – Pico de Gallo caused an outbreak that was linked to thirty seven illnesses resulting from Salmonella Paratyphi B. An advisory was never issued, likely due to the short shelf life of the product.
July – Ground beef was epidemiologically linked to eighteen illnesses caused by Salmonella Saintpaul. However, there was not enough data to identify a common source of the ground beef.
August – Ice cream contaminated with L. monocytogenes was linked to two cases of listeriosis. Whole genome sequencing (WGS) performed on the strains found in product and several environmental samples taken from the production facility indicated a match to the outbreak strain of L. monocytogenes.
August – Ground beef contaminated with E. coli O157:H7 was suspected to be involved in an outbreak, however a USDA-FSIS public health alert was not issued.
September – Watermelon and cantaloupe caused an outbreak resulting in eleven illnesses from
Salmonella Newport, however an advisory was never issued likely due to the short product shelf life.
October – Diced onions caused an outbreak resulting in eighty illnesses from Salmonella Thompson. Three water and three environmental samples collected from the farm that supplied the contaminated onions tested positive and matched the outbreak strain as determined by WGS.
November – Apple cinnamon fruit puree pouches were recalled after reports of acute lead exposure in multiple children led to an investigation and finding of extremely high concentrations of lead in multiple product lots. Since only products containing cinnamon had elevated lead levels, FDA’s leading hypothesis in the ongoing investigation is that cinnamon used in the recalled pouches is the likely source of contamination.
November – Peaches, plums, nectarines (i.e. stone fruit) were epidemiologically linked to eleven illnesses involving L. monocytogenes. Subsequent sampling and testing of 2lb bagged peaches from the supplier were found positive and linked with WGS to outbreak illnesses occurring as far back as August 2018.
November – Cantaloupe have been linked to the largest outbreak of the year, resulting in 230 illnesses and three deaths from Salmonella Sundsvall & Oranienburg infection. Additionally, 129 illnesses and five deaths reported by Canadian health officials have been linked to this outbreak.

Salmonella Outbreak Linked to Cantaloupe Products

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A new outbreak involving imported whole cantaloupe and downstream sliced/cubed cantaloupe containing products contaminated with Salmonella was posted by CDC and FDA officials on November 17, 2023. Currently, 99 individuals in the U.S. and 63 in Canada have reported illness. Initially, whole genome sequencing showed that Salmonella Sundsvall was closely related
genetically to the bacteria collected from those reporting illness. Salmonella Soahanina and Oranienburg are now also identified as outbreak strains detected in the imported product by Canadian officials. Numerous whole and sliced/cubed cantaloupe containing products have been recalled from major retailers across the U.S. and Canada.

Outbreaks involving cantaloupe are not uncommon. Contamination often begins in the field and is then spread to process/packaging facilities where it can become established in the environment. If proper controls are not in place, pathogens can spread to the edible fruit when cut and processed into ready-to eat products. This can spread to further products when cut cantaloupe is used as an ingredient. Investigation reports from three of the outbreaks highlighted in the table below are available from FDA.

Year Pathogen Product Illnesses Country
2022Salmonella Typhimuriumwhole cantaloupe87USA
2019Salmonella Javianacut fruit mix containing cantaloupe165USA
2019Salmonella Carraucut melon including cantaloupe137USA
2018Salmonella Adelaidecut melon including cantaloupe77USA
2012Salmonella Typhimurium
and Salmonella Newport		whole cantaloupe261USA
2012Listeria monocytogeneswhole cantaloupe147USA
2011Salmonella Panamawhole cantaloupe20USA
2008Salmonella Litchfieldwhole cantaloupe51USA

The following describes FDA’s investigational findings from their most recent report and provides their recommendations to growers of melons and similar produce. In August 2022, a CDC epidemiological investigation and traceback data identified a multistate cluster of Salmonella Typhimurium illnesses in the upper Midwest indicating melons as a potential source of exposures. The outbreak was traced to cantaloupe and resulted in eighty-seven illnesses and thirty-two hospitalizations across eleven states.

The FDA utilized traceback data to identify a common packinghouse of suspect cantaloupes associated with the outbreak. However, there was no convergence to a single shipment of products. Three farms in southern Indiana that supplied the common packinghouse were identified as potential sources of cantaloupe. Around the growing locations other commodities were grown such as grain, oilseed, and beans; interspersed with various vegetable crops, including melons; and several poultry feeding
operations. Heavy rains had also occurred in the growing region in late July resulting in floods.

Sampling of the packing house, the three farms, and the surrounding lands resulted in numerous findings of Salmonella, but only one of the farms produced an isolate genetically related to the outbreak strain (i.e., having an intermediate level of differences in genomes but not a genetic match). The results suggest that Salmonella presence is a reoccurring issue that may impact the safety of melons grown in this region.

FDA provides the following recommendations/requirements to producers of melons and similar produce.

  • Review current conditions and practices to determine whether they are adequate or if additional
    prevention measures are warranted.
  • Understand previous land use to identify and address potential sources of pathogens that may
    affect their farming operations.
  • Assess risks that may be posed by adjacent and nearby land uses, especially as it relates to the
    presence of livestock, poultry, and the interface between farmland, and other agricultural areas.
  • Consider additional tools such as pre-harvest and/or post-harvest sampling and testing of
    products to help inform the need for specific prevention measures.
  • Poultry manure, while valued for its fertilizer value, is a known reservoir for Salmonella
    spp. Proper application of a manure that has been treated with a validated and verified process
    to reduce pathogens (e.g., composting with time and temperature measurements) can
    significantly reduce the potential for the integration of Salmonella or other human pathogens into
    soils (as compared to the use of raw manures).
  • Inspect, maintain, and clean and, when necessary and appropriate, sanitize all food contact
    surfaces of equipment and tools used as frequently as necessary to protect against contamination.
  • When appropriate, use EPA-approved products according to the label for cleaning and sanitizing.
  • Inconsistent adherence to or deviation from existing SOPs for cleaning and sanitizing by farms can
    affect produce safety. Effective communication on farms about SOPs and any changes to those
    SOPs can help ensure that food safety practices are being followed.
  • Root cause analyses may be useful in identifying for growers how human pathogen sources in the
    broader agricultural environment may contribute to contamination.
  • Improve traceability through increased digitization, interoperability, and standardization of
    traceability records which would expedite traceback and help remove contaminated product from
    the marketplace more quickly, thereby preventing further illnesses. This is not only important for
    growers, but also critical for shippers, manufactures, and retailers as well, to improve overall
    traceability throughout the supply chain.

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