Researchers highlight past outbreaks at international event

Scientists have given details about different Staphylococcus aureus, Bacillus cereus, norovirus, and Cryptosporidium outbreaks in various countries.

Presentations at the European Scientific Conference on Applied Infectious Disease Epidemiology (ESCAIDE) covered outbreaks in Turkey, Kazakhstan, and Portugal.

In January 2023, after dinner at a factory in Turkey with 165 evening shift workers, 38 people with nausea, vomiting, abdominal pain, and facial flushing were admitted to hospitals.

Researchers collected information from 162 workers on soup, pasta, salad, fish, and halva consumption and symptoms. They interviewed the factory production manager, workplace physician and kitchen chef, and examined the seller that supplied fish to the site.

A total of 86 suspected cases were recorded. Bonito fish consumption was significantly associated with illness. Environmental investigations revealed that fish were left outside for two or three hours. Bacillus cereus was isolated from cooked fish samples. Histamine might have caused facial flushing and itching. Bacillus cereus was not isolated from stool samples.

Researchers recommended corrective measures and trained kitchen workers and the fishmonger on hygiene.

Outbreaks at restaurant and school
In February 2023, 71 hospitalized patients with gastroenteritis were reported among people who had ordered food from a delivery restaurant in Talgar, Kazakhstan.

Scientists conducted a retrospective study among people who consumed food from the restaurant from Jan. 31 to Feb. 1, 2023. Of 381 people identified, 364 were interviewed and 215 had become ill. Patients mostly had abdominal pain, diarrhea, nausea and, headache but also chills, fever, and vomiting. Mean illness duration was four days but ranged from one to eight. Risk of illness was higher among people who ate Caesar sushi, chicken pizza, and American style pizza.

E. coli and Enterococcus were detected in the sushi. Of 22 gastric samples tested from patients, scientists detected Bacillus cereus, Enterococcus, and E. coli.

An environmental assessment found several food safety violations such as improper storage conditions, prepared foods being stored with raw materials, and missing or expired workers’ health and food certifications. Because multiple pathogens were detected in food and patient samples, and disease was associated with multiple items, researchers suspected that food contaminated at different points in the preparation process was the likely source of the outbreak. The restaurant was closed and sanitized.

Also in February 2023, an acute gastroenteritis outbreak was reported at a high school in Cinfães, Portugal, affecting 52 students who had lunch in the canteen.

An investigation revealed that 123 individuals met the case definition. Vomiting was reported in three quarters of cases and more than half had diarrhea. Leftovers of the lunch including poultry rice, mushroom rice and carrot cream, tested positive for Staphylococcus aureus and Staphylococcal Enterotoxin. One food handler’s hands tested positive for Staphylococcal Enterotoxin, while surface swabs were negative. Six vomit specimens were positive for Staphylococcal Enterotoxin.

The investigation concluded the outbreak was caused by Staphylococcus, originating from the contaminated hands of a food handler, with the lunch meals serving as the vehicle.

2022 outbreaks
ESCAIDE took place from Nov. 22 to 24 in Barcelona and remotely. It was organized by the European Centre for Disease Prevention and Control (ECDC).

In late December 2022, an outbreak of gastroenteritis occurred among high school female dorm residents aged 13 to 18 years old in Turkey. The median incubation time was 19 hours but ranged from 1 to 45.

Of 127 students, 88 reported illness. The dinner served on Dec. 21 was the likely source of infection, with rice consumption being the only item significantly associated with illness. Norovirus was detected in a stool sample but the bacterial culture was negative.

“We used the findings of this study to develop targeted food safety measures, such as proper food handling and hygiene practices, to prevent and control outbreaks in similar settings,” said scientists.

Another gastroenteritis outbreak occurred at a business event in late September 2022 at a hotel in Helsinki, Finland. Out of 85 participants, 66 completed an online questionnaire and 35 met the case definition. Symptoms included diarrhea, stomach pain, and nausea.

Among patients, 34 ate a ready-to-eat (RTE) salad mix during dinner. Of 13 collected fecal samples, seven were tested for Cryptosporidium and four were positive with three characterized as Cryptosporidium parvum. No food or environmental samples were available for testing. A green salad mix was the suspected source of the outbreak.

The salad mix was purchased from a different supplier than usual and served only during dinner on one day. Traceback analysis of the suspected food item identified two batches that were processed and packed in Sweden.

Scientists said existing recommendations of storing frozen food samples at restaurants for later testing should be strengthened and risk management measures should be developed for producing RTE salads.

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