Almost 550 people were hospitalized in Vietnam earlier this year after a Salmonella outbreak linked to a type of sandwich sold at a bakery.
The outbreak occurred in Dong Nai province in May 2024. The Dong Nai Food Safety Department and the Institute of Public Health in Ho Chi Minh City investigated the incident.
A study published in the Western Pacific Surveillance and Response Journal revealed that 547 cases were recorded from April 30 to May 6. Two people were in severe condition, and a 6-year-old boy died. A total of 284 patients were female and 263 were male. The average age was 35.
Among 99 interviewed cases, the mean incubation time was 9 hours, ranging from 2 to 24 hours. The main symptoms were fever, abdominal pain, diarrhea, and vomiting.
Bakery findings
All patients had eaten banh mi from a bakery in Long Khanh City. Banh mi is a baguette sandwich filled with pate, Vietnamese pork roll, ham, pork, and pickled vegetables.
Salmonella was identified in food samples and clinical specimens. The bakery halted production, and the outbreak ended after a week. It was a takeaway shop that only sold banh mi. All four vendors and food handlers were interviewed about food processing, routine selling activities, and their history of illness. Six food samples of pate, pork, ham, pickled vegetables, and two chicken eggs were taken.
The bakery has sold banh mi for more than 20 years. Staff estimated that around 1,500 banh mi were sold from April 30 to the morning of May 1. The bakery made the pate, pickled vegetables, and sauces. The remaining foods were bought from a third-party supplier.
An investigation found that the bakery did not follow the one-way principle for food processing. All the processes overlap in the cooking stages, and contact between raw and cooked foods could occur. Areas for preparing raw and cooked foods were next to each other, and there was no table or food storage shelf. The staff did not wear gloves. The food and raw materials were put on the floor or in two cold stores.
Positive food and fecal samples
Salmonella was found in 12 of 25 fecal specimens and four food samples. Both fecal specimens from staff were positive for Salmonella. Two food samples were contaminated with Staphylococcus aureus and one with Bacillus cereus.
“Most food samples were positive for Salmonella, indicating that all foods could be cross-contaminated due to poor hygiene practices. The results of the environmental investigation supported this assumption. An asymptomatic carrier was possibly the cause of the outbreak. However, they could have been infected through the same sources as the patients,” said researchers.
In Vietnam, foodborne illness affected 3,711 people from March 2020 to August 2022. An outbreak in Khanh Hoa was reported in 2024, with 345 cases linked to contaminated chicken rice at a restaurant. Vietnam lacks annual salmonellosis data due to the absence of a reporting system.
“This outbreak reminds small retailers and takeaway shops of the importance of food safety management in preventing similar future outbreaks. All food handlers must comply with food hygiene principles, especially in hot temperatures, which boosts bacterial growth,” said scientists.
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