Federal, state, and local officials investigated dozens of foodborne outbreaks during 2023, with some ongoing as the year ended.

One common denominator among the outbreaks is that far more people are likely to have gotten sick than were confirmed ill in each outbreak. based on its research, the Centers for Disease Control and Prevention reports that for every confirmed case of Salmonella, there are 29 patients. For E. coli, that number is 26 for the Shiga toxin-producing O157 strain and 106 for the Shiga toxin-producing non-O157 strain. For Listeria monocytogenes, two cases generally go undetected for every confirmed patient.

The reasons behind the numbers include many people not seeking medical treatment because they think they have a “stomach bug” and others not being correctly diagnosed by healthcare providers because specific pathogen testing is not ordered.

Deadly cantaloupe outbreak
The most recent outbreak in the headlines is ongoing and has been traced to whole cantaloupe from Mexico. The recalled cantaloupe has been used in a wide variety of fresh-cut products that have also been recalled.

The deadly outbreak spans the border, with patients having been documented in the United States and Canada. As of late December, there were 302 people infected in the United States, with four having died. In Canada, there are 164 sick people, with seven having died. 

Investigators from the U.S. Centers for Disease Control and Prevention, the U.S. Food and Drug Administration, the Public Health Agency of Canada, and the Canadian Food Inspection Agency continue identifying patients and other potentially contaminated products.

Another ongoing outbreak involves lead poisoning traced to cinnamon applesauce pouches marketed particularly for children. The number of children affected by the extremely high levels of lead in cinnamon in the applesauce pouches continues to grow, and some adults are now reported in the outbreak. 

The outbreak has been traced to three brands of cinnamon applesauce: Wanabana, Schnucks, and Weis. Astrofoods produced all three in Ecuador and used cinnamon from the supplier Negasmart. The recalled cinnamon applesauce pouches were made with cinnamon containing as much as 2,000 times the recommended amount of lead. 

The cinnamon in the applesauce is a problem for U.S. and Ecuadorian officials. The U.S. Food and Drug Administration is testing other products. As of Dec. 26, the Food and Drug Administration reported receiving 82 reports of affected people. As of Dec.22, the CDC had received reports of 73 confirmed cases, 157 probable cases, and 21 suspected cases for 251 cases from 34 states. The CDC and FDA have separate reporting systems, so there may be some overlap, meaning the total numbers from the agencies should not be added together.

An outbreak of infections from Listeria has been traced to fresh peaches and sparked a recall of whole, fresh peaches, plums, and nectarines. Eleven confirmed patients have been reported across seven states. One patient has died. The peaches, plums, and nectarines were sold in retail stores between May 1 and November 15, 2022, and between May 1 and November 15, 2023. The fruit was sold as individual pieces and in plastic pouches. The outbreak is an example of how investigators use whole genome sequencing of pathogens and a national database to identify patients in a single outbreak spread across time and distance.

As of the end of this year, the FDA is investigating at least two outbreaks of unknown origin. A Listeria outbreak first reported on Dec. 6 has sickened at least three people, and a Salmonella outbreak first reported by the FDA on Nov. 22 has sickened at least 44 people. The agency has not provided any further details on the two outbreaks.

Salmonella outbreak linked to dog food — An ongoing investigation into an outbreak of human Salmonella infections traced to dog food has identified seven patients in seven different states, according to the CDC. One patient has been hospitalized. The age range of known patients is younger than 1 to more than 65 years old. As with all outbreaks, the true number of sick people in this outbreak is likely much higher than the number reported, and the outbreak may not be limited to the states with known illnesses, according to the CDC. The outbreak has been linked to various varieties of Victor brand dog food.

A Canadian outbreak of particular note was traced to meatloaf and vegan loaf served by a central kitchen serving several daycare centers. The investigation closed in October. As of Sept. 27, 351 children were confirmed sick in the E. Coli O157:H7 outbreak. The outbreak saw 37 hospitalized, with 22 children diagnosed with hemolytic uremic syndrome (HUS), which attacks the kidneys and bloodstream and can lead to multiple organ failure, brain damage, and the need for transplants.

FDA unresolved sources
Eight investigations by the FDA have been closed this year without the source being found—four of those involved E. coli infections, with a total of 74 people sickened. Salmonella caused one outbreak. It sickened 54 people. One outbreak of Cryptosporidium of unknown origin was reported, with 11 confirmed patients. Three outbreaks from unknown sources of cyclospora were investigated. They sickened a total of 271 people.

Other 2023 outbreaks of note — in no particular order
This year, they continued a decades-long string of infections from unpasteurized, raw milk. At one point this fall, four states’ authorities were investigating outbreaks. Most of the time, investigations linked to raw milk outbreaks do not involve federal authorities because selling raw milk across state lines is illegal. Here are details on four known outbreaks reported in September and October:

• Public health officials in Salt Lake County reported an outbreak of campylobacter infections associated with raw, unpasteurized milk. The Salt Lake County Health Department confirmed at least 14 people with infections. Twelve of the patients reported drinking raw milk before becoming sick, according to a notice from the department. The department reported that the patients ranged from 2 to 73 years old. One of them was hospitalized.

• The Wyoming Department of Health confirmed that two children were hospitalized after drinking raw milk in September. Five people, one adult and four children, became ill after drinking raw, unpasteurized milk purchased through the Slow Food in the Tetons online market. The patients were infected with campylobacter and E. Coli bacteria.

• Nine people were sickened, and three were admitted to hospitals after drinking raw milk and becoming infected by Salmonella. Health officials from the County of San Diego linked the nine patients to unpasteurized milk sold by Raw Farm LLC in Fresno. The nine San Diego County residents who became ill reported consuming Raw Farm LLC raw milk or milk products the week before their illness onset. The patients range in age from 1 to 41 years old. All three of the hospitalized patients were children.

• State health officials in Idaho investigated a cluster of illnesses believed to be associated with the consumption of unpasteurized, raw milk. Central District Health announced reports of illness in five Ada County residents who drank raw milk. Three of the five individuals tested positive for campylobacteriosis, a bacterial infection and reported drinking raw milk produced by Provider Farms in Mountain Home before getting sick.

Cyclospora —  An outbreak of infections from the cyclospora parasite has been declared over by the Centers for Disease Control and Prevention, with more than 2,000 patients logged. The CDC first reported the outbreak on May 25. As of Oct. 24, the agency reported 2,272 laboratory-confirmed patients from 40 states. “These individuals had not traveled outside of the United States during the 14 days before they got sick,” according to the CDC. Sick people ranged in age from 2 to 96 years, with a median age of 51. Of 2,242 people with information available, 186 were hospitalized.

Cantaloupe August-September — First posted on Aug. 17 by the Food and Drug Administration, there was little information on the outbreak, except for the patient count, which was 87 people across 11 states.

Listeria monocytogenes in leafy greens — An outbreak of infections from Listeria monocytogenes in leafy greens sickened 19 people across 16 states, with 18 of the patients requiring hospitalization. Of 14 people with complete information available, 13 reported eating leafy greens before becoming sick. No specific brand of leafy greens was determined. It is particularly difficult to identify sources of Listeria infection because it can take up to 70 days for symptoms to develop.

Salmonella in onions — As of Dec. 4, 2023, the CDC announced that an outbreak from Gills brand diced onions was over. The agency reported a total of 80 illnesses in 23 states. There was a total of 18 hospitalizations and one death associated with the outbreak. The last illness onset was Nov. 11. There is some concern that consumers may have frozen the onions for future use.

 Salmonella in raw cookie dough — The CDC reported that 26 people were confirmed as part of the outbreak, four requiring hospitalization. Papa Murphy’s raw cookie dough was identified as the source of the pathogen. According to the CDC, Illnesses started from Feb. 24 to May 28.

Salmonella in ground beef — The CDC declared an outbreak of Salmonella Saintpaul infections over, with 18 sickened people from four states. According to a notice from the Centers for Disease Control and Prevention, investigators linked the outbreak to ground beef sold at ShopRite stores in the Northeast. Seven of the 18 patients were so sick they had to be hospitalized. Patients were from four states. No one died.

Salmonella in raw flour — In April, the CDC announced 14 patients across 13 states from coast to coast were infected. Three were hospitalized. Gold Medal Flour from the same plant linked to a 2016 E. Coli outbreak that sickened 38 people across 20 states was determined to be the source of the Salmonella.

Hepatitis A virus in frozen strawberries — Ten patients in four states were identified, with four requiring hospitalization. Frozen organic strawberries imported from Baja California, Mexico, were determined to be the source of the virus. Additionally, the strain of hepatitis A virus causing illnesses this year was genetically identical to the strain that caused an outbreak of hepatitis A virus infections in 2022, which was linked to fresh organic strawberries imported from Baja California, Mexico, and sold at various retailers. Investigators found that a single farm was associated with the distribution of strawberries consumed by ill people in both outbreaks.

Campylobacter in oysters — The FDA has warned about certain oysters harvested in Canada and sold in the United States because two people have become infected with Campylobacter jejuni. On Dec. 18, the Utah Shellfish Authority notified the Food and Drug Administration of two cases of Campylobacter connected to consumption of oysters from British Columbia, Canada. The FDA has notified the Canadian Food Inspection Agency (CFIA) of the illnesses, and that agency is investigating. The two patients consumed oysters in Utah and Wisconsin, and the FDA is coordinating with the CFIA and state authorities to determine if any additional distribution occurred.

Listeria and ice cream — The Food and Drug Administration confirmed that “On the Go” ice cream cups were behind foodborne illnesses in two states. The ice cream made by Real Kosher Ice Cream of Brooklyn, NY, was contaminated with the same strain of Listeria monocytogenes as found in samples from two patients. Both patients, one in New York and the other in Pennsylvania were so sick that they required hospitalization.

Outbreaks associated with schools and restaurants

Norovirus and sushi restaurant — As of the second week of December, authorities reported 241 complaints from patrons of Nine Sushi, a restaurant in Raleigh, NC. The complaints began Nov. 28, according to local health department officials. The suspected pathogen was norovirus, with at least three restaurant customers testing positive. The restaurant closed temporarily for cleaning.

Huntley High School and E. coli — An infected food handler has been identified as the most likely source of an E. coli outbreak at an Illinois high school that saw 16 students sickened and two hospitalized. A breakdown in hand-washing protocol was the most likely cause of the illnesses, according to a 152-page report from the McHenry County Department of Health. An infected food handler was identified by laboratory testing of stool samples.

Chicago area restaurant and Salmonella — At least 55 people were infected with Salmonella after eating food from a Chicago taqueria. Ten people were hospitalized. The Chicago Department of Public Health and the Illinois Department of Public Health investigated the outbreak. The agencies reported that Carniceria Guanajuato voluntarily closed the taqueria for cleaning.

University of Arkansas and E. coli — Public health officials closed an investigation into an E. Coli outbreak at the University of Arkansas without finding the source of the pathogen. University officials said the Arkansas Department of Health reported five confirmed and 37 probable patients in the outbreak. On Sept 25, university officials said more than 3,200 people had been surveyed during the investigation. The outbreak was reported on Sept. 1, but no patients were identified after Aug. 25. Four confirmed patients were hospitalized.

Sushi restaurant and mushrooms — At least 30 people were sickened and two people died after eating at a restaurant in Montana. The restaurant was Dave’s Sushi in Bozeman, MT. People who became ill generally had symptom onset between 30 minutes and 4 and a half hours after eating at the restaurant. Health department officials report that the implicated mushrooms were imported. The mushrooms were cultivated in China, shipped to a distributor in California, and subsequently sent to multiple states.