Epidemiology and Health

Epidemiologic Investigations

Workplace outbreak of enterotoxigenic Escherichia coli O159 enteritis linked to kimchi consumption in Daejeon, Korea, 2024: Ji Hae Hwang, Eun Mi Song, Eun Ho Jeong, Joo Yeon Kim, Jin Hee Kim, Hyun Jin Kim, Soyeon Nam, Jiyeon Cheon, Eunkyung Shin, Wooju Kang, Junyoung Kim, Hae-Sung Nam; Epidemiol Health. 2026;48:e2026031. Published online June 22, 2026; DOI: https://doi.org/10.4178/epih.e2026031

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Abstract Summary PDF: Abstract
OBJECTIVES
In August 2024, a large outbreak of gastrointestinal illness was reported among workers at a workplace in Daejeon, Korea, where bulk meals were served. This study investigated the epidemiological and microbiological characteristics of the outbreak to identify the causative pathogen, the infection source, and possible contamination routes.
METHODS
A comprehensive epidemiological investigation was conducted, including case identification, retrospective cohort analysis, laboratory confirmation, and pulsed-field gel electrophoresis (PFGE). Attack rates, relative risks (RRs), and 95% confidence intervals (CIs) were calculated. Environmental and distribution chain assessments were also performed to trace the sources and transmission pathways.
RESULTS
A total of 77 individuals met the case definition, including 75 symptomatic cases and 2 asymptomatic food handlers who tested positive for enterotoxigenic Escherichia coli (ETEC) O159. Among the 75 symptomatic cases, 25 were laboratory-confirmed, resulting in a total of 27 laboratory-confirmed cases. The mean and median incubation periods were 70.5 hours and 72.0 hours, respectively. The attack rate was significantly higher among kimchi consumers than among non-consumers (RR, 1.47; 95% CI, 1.08 to 2.00). PFGE identified ETCX01.332 as the predominant pattern among patient and kimchi isolates. Distribution tracing indicated that the implicated kimchi was produced at a factory in Gyeonggi Province and supplied to multiple catering facilities, leading to additional outbreaks in Seoul and Gyeonggi Province. However, the exact contamination point(s) during production or distribution remained undetermined.
CONCLUSIONS
This outbreak was attributed to ETEC O159, with kimchi suspected as the infection source. These findings provide rare evidence implicating non-heated fermented foods in ETEC transmission and highlight the need for strengthened hygiene standards and real-time monitoring throughout the production, distribution, and handling of fermented foods.; Summary

Korean summary
본 연구에서는 대전 소재 사업장에서 발생한 ETEC O159 집단발생에 대한 역학조사와 미생물학적 분석을 통해 김치를 가장 유력한 원인식품으로 추정하였다. 환자와 보존식 김치 분리주에서 동일한 PFGE 유형이 확인되었고, 동일 제조업체의 김치를 공급받은 서울과 경기 지역에서도 관련 집단발생이 확인되었다. 이는 비가열 발효식품의 광역 유통이 여러 지역의 집단발생으로 이어질 수 있음을 보여주며, 제조·유통 전 과정의 위생관리와 모니터링 강화가 필요함을 시사한다.

Key Message
This study provides epidemiological and molecular evidence that kimchi contaminated with ETEC O159 was the most likely vehicle of a workplace outbreak, with identical PFGE patterns identified in patient and preserved-kimchi isolates. Traceback investigations linked contemporaneous outbreaks in Daejeon, Seoul, and Gyeonggi Province to kimchi from the same manufacturer. These findings address a gap in evidence on ETEC transmission through non-heated fermented foods and highlight the need for strengthened hygiene control and real-time monitoring throughout production and distribution.

Salmonellosis outbreaks linked to eggs at 2 gimbap restaurants in Korea: Jun Suk Eun, Joohyun Han, Ji-Hyun Lim, Eunkyung Shin, Junyoung Kim, Da-Jung Ko, Jaeil Yoo, Sungil Kim, Jin Sook Kim, Jung Sub Park, Ji-Hyuk Park; Epidemiol Health. 2024;46:e2024036. Published online March 7, 2024; DOI: https://doi.org/10.4178/epih.e2024036

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9 Web of Science
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Abstract Summary PDF Supplementary Material

Abstract

OBJECTIVES
Salmonellosis outbreaks occurred at 2 restaurants 2 days apart, and an epidemiological investigation was conducted to determine whether the outbreaks were connected.

METHODS

Case studies were conducted for both outbreaks. Stool samples were collected from individuals, and food samples were collected from the restaurants. Pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing analyses were performed on outbreak-related Salmonella enterica serovar Enteritidis (Salmonella Enteritidis) isolates. Traceback investigations were also conducted for the ingredients from gimbap restaurants A and B.

RESULTS

In total, 106 people from gimbap restaurant A and 5 from gimbap restaurant B met the case definition. Salmonella Enteritidis was detected in samples from 2 food handlers, 22 patients, and 1 food (iceberg lettuce) at gimbap restaurant A and from 1 patient at gimbap restaurant B. According to PFGE, all isolates were identified as SEGX01.089. The molecular typing of all isolates showed the same pattern, and the genetic distance was close according to phylogenetic analysis. Eggs were the only food ingredient that was supplied to both gimbap restaurants.

CONCLUSIONS

The outbreaks were caused by Salmonella Enteritidis, and the source of infections was suspected to be contaminated eggs. To prevent foodborne outbreaks of Salmonella, restaurants should heat eggs sufficiently, and egg farms need to establish management systems that prevent Salmonella infections.

Summary

Korean summary
동일한 도시의 두 식당에서 2일 간격으로 살모넬라감염증 유행이 발생하여, 원인을 확인하고 두 유행 간에 연관이 있는지를 규명하기 위해 역학조사를 시행하였다. 병원체에 대한 유전자형 분석과 식재료 역추적조사 결과를 바탕으로 두 유행은 Salmonella Enteritidis에 의해 발생하였고, 감염원은 동일한 농장에서 공급된 오염된 계란으로 추적하였다.

Key Message
Salmonellosis outbreaks occurred at 2 restaurants in the same city 2 days apart, and epidemiological investigations were conducted to identify the causes and determine whether the outbreaks were connected. Based on the genetic characterization of the pathogens and traceback investigation of the food ingredients, the outbreaks were caused by Salmonella Enteritidis and the source of infection was traced to contaminated eggs, which were supplied from the same farm.

Citations

Citations to this article as recorded by

Product-specific microbial community dynamics in egg-based processed foods: Integrated analysis of processing facility environments and retail products
Young Eun Moon, Ji Won Lee, Ju Yeon Song, Tae Jin Cho, Min Suk Rhee, Sun Ae Kim
International Journal of Food Microbiology.2027; 462: 112069. CrossRef
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Su Jin Jo, Sang Guen Kim, Sib Sankar Giri, Sung Bin Lee, Jae Hong Park, Mae Hyun Hwang, Da Sol Park, Eun Jae Park, Se Chang Park
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Emerging Infectious Diseases.2025;[Epub] CrossRef
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Ling Zhang, Mingqiang Guo, Xiaoyu Ma, Wei Wang, Wanpeng Ma, Yifan Liu, Junxiang Wei, Zhanqiang Su
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Journal of Yeungnam Medical Science.2025; 42: 65. CrossRef
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Journal of Innovation Food and Animal Science (JIFAS).2025; 1(2): 43. CrossRef
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Public Health Weekly Report.2024; 17(45): 1941. CrossRef

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