Nearly 550 people were hospitalized in Vietnam earlier this year after a Salmonella outbreak linked to a type of bun sold in a bakery.
The outbreak occurred in May 2024 in Dong Nai province. The Dong Nai Food Safety Department and the Ho Chi Minh City Institute of Public Health investigated the incident.
A study published in the Western Pacific Surveillance and Response Journal revealed that 547 cases had been recorded between April 30 and May 6. Two people were in serious condition and a 6-year-old boy died. A total of 284 patients were female and 263 were male. The average age was 35 years.
Of the 99 cases interviewed, the average incubation period 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 filled with pate, Vietnamese pork roll, ham, pork and pickled vegetables.
Salmonella was identified in food samples and clinical samples. The bakery stopped production and the outbreak ended after a week. It was a take-out shop that only sold banh mi. All four salespeople and food handlers were interviewed about food handling, routine sales activities, and their medical history. Six food samples were taken of pate, pork, ham, pickled vegetables and two chicken eggs.
The bakery has been selling banh mi for more than 20 years. Staff estimated that approximately 1,500 banh mi were sold between April 30 and the morning of May 1. The bakery made the pate, pickled vegetables and sauces. The remaining foods were purchased from an external supplier.
Investigation revealed that the bakery did not follow the one-way food processing principle. All processes overlap in the cooking phases and contact can occur between raw and cooked food. The areas for preparing raw and cooked food were next to each other and there was no table or shelf for food storage. The staff did not wear gloves. The food and raw materials were placed on the floor or in two cold rooms.
Positive food and fecal samples
Salmonella was found in 12 of 25 fecal samples and four food samples. Both staff stool samples 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 can become cross-contaminated due to poor hygiene practices. The results of the environmental study supported this assumption. Asymptomatic carrier status may have been the cause of the outbreak. However, they may have been infected through the same sources as the patients,” researchers said.
In Vietnam, foodborne illness affected 3,711 people between March 2020 and August 2022. In 2024, an outbreak was reported in Khanh Hoa, with 345 cases linked to contaminated chicken rice at a restaurant. Vietnam does not have annual data on salmonellosis due to the lack of a reporting system.
“This outbreak is a reminder to small retailers and takeaways of the importance of food safety management in preventing similar future outbreaks. All food handlers must adhere to the principles of food hygiene, especially at high temperatures, which encourage the growth of bacteria,” scientists said.
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