Almost 20 people have fallen ill in Sweden this month from histamine poisoning in fish from Vietnam.

The foodborne outbreak at the beginning of April affected 19 people in Stockholm.

Guests eating tuna at three different restaurants in Stockholm reported symptoms of histamine poisoning.

All three restaurants purchased frozen tuna loins with the same expiry date from the same supplier, indicating that high levels of histamine occurred before the tuna was brought into Sweden from Vietnam via the Netherlands.

Recurring issue
In March, Italian authorities reported an outbreak caused by histamine in frozen yellowfin tuna loins from Vietnam, via the Netherlands but did not say how many people were affected.

In 2020, Sweden recorded three outbreaks of histamine poisoning in tuna from Vietnam in three months.

These outbreaks affected about 60 people but were not directly related as the tuna originated from different batches. Patients were from different areas in southern and central Sweden.

Onset of histamine food poisoning symptoms can range from minutes to several hours following ingestion of the toxin. Typically, the average incubation period before illness is one hour.

The most common symptoms of histamine, also known as scombroid fish poisoning, are tingling or burning sensation in the mouth, facial swelling, rash, hives and itchy skin, nausea, vomiting or diarrhea. They usually resolve within several hours without medical intervention.

Production of histamine is related to mishandling of food because of storage at incorrect temperatures. Once produced, histamine cannot be eliminated by normal cooking or freezing temperatures.

New rules and Salmonella study
Meanwhile, new legislation has come in from this month in Sweden that includes food control authorities being able to make purchases without disclosing their identity as an official agency until afterward. This makes it easier to check that food on the market is what it claims to be, does not mislead consumers, and that it is not harmful to health.

It applies to distance purchases such as e-commerce and to physical stores. Previously, there had been no support in law for authorities to act without making themselves known. The changes were made to bring domestic rules into line with EU regulations.

Finally, the government has commissioned the Swedish Board of Agriculture and Swedish Veterinary Institute to do a feasibility study on measures to effectively prevent and manage the presence of Salmonella in farm animals.

In the past year, the number of Salmonella cases has increased in food-producing animals and in pig herds. This leads to increased costs for animal owners and the state in combating outbreaks.

The work will investigate possible sources of infection and include new knowledge on analysis methods. Findings will be reported by the end of January 2022.

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