Salmonella Agbeni Outbreak Linked to Ice in a County Fair Beer Cooler — Illinois, 2024

A report in CDC's Morbidity and Mortality Weekly Report by Katherine E. Houser of the Brown County Health Department, Mount Sterling, Illinois.

In brief

• What was known: Salmonella usually spreads through contaminated food or water, or contact with infected people or animals.
• What this adds: at an Illinois county fair in August 2024, 13 cases of Salmonella enterica serotype Agbeni — seven confirmed, six probable — were linked to ice contaminated while beverage cans were handled in a beer cooler. Ice is an uncommon vehicle for Salmonella at public events. An artificial-intelligence tool helped gather background to support the team's assessment; every epidemiologic conclusion rested on ordinary methods — interviews, laboratory confirmation and environmental findings.
• What it means: standard, robust hygiene rules for cleaning coolers and handling ice and drinks at events might prevent similar outbreaks.

The fair

The Brown County Fair is held every year in Mount Sterling, Illinois, a rural, close-knit community of about 4,200 people. It draws an estimated 36,000 visitors a year, about 5,000 a day. Most watch the evening events from a grandstand seating about 3,000.

In front of the grandstand is the infield, reserved for premier ticket holders, who may park flatbed trailers there to tailgate. It had food vendors, a single beer tent open only to people with wristbands showing they were 21 or older, several portable toilets and a few portable handwashing stations. The 2024 fair ran July 30 to August 4; the beer tent was staffed by a rotating committee of volunteers and fair board members, many of whom handled drinks and ice.

How it came to light

• August 5, the day after the fair ended: the county sheriff told the health department that many potential jurors, screened for an upcoming trial, had reported a recent stomach illness. Confidentiality rules meant no names were given, and no investigation began.
• August 12: the Illinois Department of Public Health reported a laboratory-confirmed S. Agbeni infection — a nontyphoidal Salmonella — to the county. By then the fair was over and the venue could not be sampled. With the jurors' reports, the result prompted a formal outbreak investigation.

A confirmed case followed CDC's definition: an illness consistent with salmonellosis — diarrhoea, abdominal pain, nausea, sometimes vomiting — with Salmonella grown from a clinical specimen. A probable case was a consistent illness linked to a confirmed case, for example through a shared exposure at the fair, without a culture, including a positive PCR test not confirmed by culture. The work was public health practice, not research.

Who got sick

• Seven confirmed cases, found through the National Electronic Disease Surveillance System, in residents of five Illinois counties who had been to the fair.
• Six probable cases in close contacts, found through interviews. They had milder symptoms — nausea and diarrhoea — and sought neither testing nor care. Two were spouses of confirmed cases.
• All 13 were aged 23 to 53; ten were men and three women.

Ruling things out

Investigators first suspected vendor food or the shared portable toilets. All 13 answered the state's foodborne illness questionnaire:

• nine had bought food from one or more of six different vendors on different days — and four had eaten nothing at the fair;
• two cleaned their hands with their own sanitiser, and ten did not wash their hands;
• four never used the portable toilets;
• none sat in the grandstand or worked in the livestock barns.

But all 13 had spent time in the infield and drunk canned beer from the beer tent, and no one who had not used the beer tent was found to be ill.

The cooler

Beer-tent workers described the cooler:

• a 10-foot length of non-food-grade corrugated black plastic farm drainage tile with four compartments, meant to hold only ice and cans;
• ice from a single local company, made from municipal water, and supplied to every vendor at the fair;
• rinsed with a hose once, at the start of the week, never again, and never washed with soap; no way to check its internal temperature;
• ice and cans handled with bare hands, with no handwashing station in the tent;
• cans kept under ice, and the melted ice topped up daily;
• designed to drain through one spigot, but standing water was reported, pointing to poor drainage.

Different people worked the tent each night. Two of them later tested positive; both had drunk beer at the tent, and they were the only staff who reported illness. The standing water was mentioned only after the fair, and neither it nor the cooler could be tested. No cleaning routine for the cooler was reported.

The county's food inspector confirmed that ice can be contaminated if handled or stored badly; the Illinois Food Code treats ice as food. A systematic review covering 2013–2023 found food ice contaminated with gut bacteria, viruses and fungi, most often from poor ice-machine cleaning and handling, and more often in ice made on site than in factory ice.

One confirmed patient said leftover food had been stored overnight in the ice cooler on August 1. Fair board members said that was not allowed; it could not be verified, but food kept in drinks ice is a possible route for cross-contamination. Some attendees were reluctant to give details for fear of implicating neighbours.

Looking for more cases

From August 12 to 21 staff contacted fair board members and people they knew had attended, and watched social media posts and photos, asking about the beer tent and any illness. No further cases were found.

Where the AI tool came in

With the ice, water and cooler gone, and no other shared exposure, contaminated ice was already a plausible source. On August 21 the team entered the cases' details — when each fell ill, where they bought food, what they ate and drank, infield or grandstand — into a generative AI model (ChatGPT 4.0, OpenAI) and asked a series of questions. The answers, in short: S. Agbeni could grow in a poorly drained cooler on hot days; contaminated meltwater on the cans, then hand to mouth, was a plausible route; with no common food, ice fitted the facts best; dose, can handling and water temperature could explain why only some fell ill; and published outbreaks had been tied to contaminated ice, often an overlooked vehicle.

The report stresses that the tool was used only to summarise published investigations and literature, to support a hypothesis the environmental health team had formed independently — not for case finding, exposure assessment or data analysis — and that every AI summary was checked against the primary literature.

What changed

The Brown County Health Department:

• wrote guidance on cooler sanitation and safe drink handling, and sent it to every vendor, organiser and community partner;
• contacted fair board members, food handlers and volunteers about hygiene and safe food storage;
• required routine bleach sanitising of ice coolers; drink-service equipment is subject to inspection and may be barred if it falls short;
• strengthened coordination between agencies for future events;
• keeps watch during large gatherings, with food-safety audits and random checks;
• made cooler sanitation protocols a required part of future vendor licences.

Discussion

Salmonella is a leading cause of bacterial foodborne illness in the United States, usually tied to meat, produce, eggs and other higher-risk foods; here the pattern of eating pointed away from food. Because all the fair's ice came from one supplier, from municipal water, and went to every vendor, contamination at the source was thought unlikely. More plausibly the ice was contaminated after delivery: by food stored in the cooler, or from hands in the absence of handwashing. Improvised equipment that could not drain properly likely contributed. Contaminated ice has been implicated in outbreaks of norovirus, Cryptosporidium and E. coli, but Salmonella is rarely spread this way — which is why uncommon exposures deserve a place in an investigation.

Limitations

• The gap between the fair's end and the first report made finding more cases hard.
• The cooler could not be tested, so ice cannot be proved to be the source.
• Mild illness and little awareness that it should be reported probably meant cases were missed.

Knowing the community helped find cases quickly, but also made people wary of naming friends or neighbours. The lesson for similar events: enforce food sanitation and hygiene — proper ice handling and storage, frequent cooler cleaning, and keeping food and drinks ice apart.

Sources

• Houser KE. "Multicounty Outbreak of Salmonella Agbeni Linked to Ice in a Cooler at a County Fair — Illinois, August 2024." Morbidity and Mortality Weekly Report. https://www.cdc.gov/mmwr/volumes/75/wr/mm7507a1.htm
• Acknowledged: the Adams, Cass, Pike and Schuyler county health departments; the Illinois Department of Public Health and its Division of Laboratories.
• The report's case table is not reproduced here.
• One mention of the serotype in the report's question list reads "S. Abegni"; it is Agbeni throughout this page.
• Words on this page from people and organisations outside the federal government are paraphrased; rewritten in hubnx's own words.