An Outbreak Investigation of Scombrotoxin Fish Poisoning Illnesses in the United States Linked to Yellowfin Tuna Imported from Vietnam – 2019

Scombrotoxin fish poisoning (SFP) is caused by the ingestion of certain fish species with elevated levels of histamine due to decomposition. In the fall of 2019, the Food and Drug Administration (FDA) was notified of 51 SFP illnesses including two hospitalizations from 11 states through consumer complaints received by FDA’s Consumer Complaint System or directly from state partners. A case was defined as an individual who experienced a histamine-type reaction after consumption of tuna imported from Vietnam and an illness onset between August 14, 2019 and November 24, 2019. A traceback investigation was initiated at 19 points-of-service (POS) to identify a common tuna source. FDA and state partners collected a total of 34 product samples throughout the distribution chain including from a case patient’s home, POS, distributors, or at the port of entry. Samples were analyzed by sensory evaluation and/or chemical testing for the presence of histamine. Cases reported exposure to tuna imported from Vietnam. The traceback investigation identified two Vietnamese firms as the sources of the tuna. Twenty-nine samples were confirmed as decomposed by sensory evaluation and/or positive for the presence of elevated levels of histamine by chemical testing. Both Vietnamese firms were placed on Import Alert. Seven U.S. firms and one Vietnamese firm initiated voluntary recalls. FDA released public communication naming the U.S. importers to help suppliers and distributors to identify the product and as a result, effectuate the foreign firm’s recall. This SFP outbreak investigation highlights the complexities of the federal outbreak response, specifically related to imported food. Imported foods present cultural considerations that need to be addressed during outbreak response when timing is critical. Furthermore, collaborating with countries where confidentiality agreements are not in place can limit information sharing and the speed of public health response efforts.