Thirty people in Sweden fell ill with scombroid poisoning after eating tuna from Vietnam earlier this month.

The histamine poisoning foodborne outbreak was linked to frozen tuna loins from Vietnam, via the Netherlands.

Local authorities were responsible for the outbreak investigation and tracing of food batches. The Swedish Food Agency (Livsmedelsverket) is the national contact point for Europe’s Rapid alert System for Food and Feed (RASFF).

Mats Lindblad, from the Swedish Food Agency, said about 30 people were sick but no deaths were reported.

“Symptoms were typical for histamine poisoning and included swelling, hives, irregular heartbeat, nausea, diarrhea and vomiting,” he told Food Safety News.

“All reported cases had consumed a dish with tuna at the same restaurant. The outbreak occurred at the beginning of May. The link to the tuna loins is based on the epidemiological outbreak investigation. Samples have been taken from the incriminated batch, but results are pending.

“Thirty people is more than usual for a histamine outbreak in Sweden — normally reports of histamine food poisoning concern single cases or a few persons only. Normally the agency receives reports of around ten outbreaks or single cases each year.”

Distribution of the frozen tuna loins also included Austria, Cyprus, Germany, Hungary, Netherlands, Poland, Romania and Slovakia, according to the RASFF portal.

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

The most common symptoms of histamine or 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. If symptoms are severe an individual should seek medical attention for treatment. They can be treated with antihistamines.

Production of histamine is related to mishandling of food due to storage at incorrect temperatures. once histamine has been produced, it cannot be eliminated by normal cooking or freezing temperatures.