High prevalence of asymptomatic Enterotoxigenic Escherichia coli carriers among food handlers in a hospital foodborne outbreak

Enterotoxigenic Escherichia coli (ETEC) commonly causes diarrheal disease, but little is known about the contribution of asymptomatic carriers to foodborne outbreaks. We investigated an ETEC outbreak at a 760-bed hospital in South Korea in June 2024. A confirmed cases were defined as an individual with ETEC detection by PCR and gastrointestinal symptoms or fever. We screened all 61 food handlers for ETEC regardless of whether they had symptoms, and we sampled environmental surfaces and preserved food items. Of 1606 employees, 77 met the symptomatic case definition. The most frequent symptoms were diarrhoea (98.7%), abdominal pain (87.0%), and fever (28.6%). Cold buckwheat noodles were identified as the probable vehicle in multivariable analysis (adjusted OR=3.00, 95% CI 1.34-6.55, p = 0.006). ETEC was not recovered from any environmental or food samples. Among 61 food handlers, 13 asymptomatic cases were identified. (21.3%, 13/61) and only two of them had eaten cold buckwheat noodles. Kitchen inspection revealed inadequate handwashing station capacity. A 21.3% asymptomatic carriage rate among food handlers point to a contamination route that symptom-based screening would miss. Strict hand hygiene is especially important when handling cold dishes without further heat treatment.