Foodborne Disease Outbreaks Associated with Marine Toxins - Foodborne Disease Outbreak Surveillance System, United...

Marine toxins cause most of the noninfectious outbreaks reported to CDC's Foodborne Disease Outbreak Surveillance System (FDOSS) each year. Certain marine toxins are produced by algae that accumulate in aquatic animals through the food chain, whereas others appear as a result of improper food storage and are therefore preventable. Overgrowths of toxin-producing algae (harmful algal blooms) have occurred on both U.S. coasts; the historical geographic range for some species (e.g., Gambierdiscus in tropical and subtropical regions) have expanded. Marine toxins that cause foodborne illness are tasteless, odorless, resistant to cooking or freezing, and can produce a complex variety of gastrointestinal, neurologic, and neuropsychologic symptoms. Among persons with severe illness resulting from ingestion of marine toxins, cardiovascular and respiratory manifestations can result in hospitalization and death. Analyzing these outbreaks provides insight into their incidence, severity, and key characteristics, which can be used to guide food safety and foodborne illness prevention efforts.

2011-2023.

Via FDOSS, CDC collects data on foodborne disease outbreaks from local, state, and territorial health departments in the United States. Foodborne disease outbreaks are defined as two or more cases of similar illness associated with a common food exposure; outbreak etiologies and food sources can be reported as confirmed or suspected. Since 2009, health departments have voluntarily reported foodborne disease outbreaks to FDOSS through CDC's web-based National Outbreak Reporting System.

During 2011-2023, a total of 402 foodborne disease outbreaks caused by marine toxins were reported to FDOSS. These outbreaks resulted in 1,280 illnesses, 96 hospitalizations, and one death. The national rate of these reported outbreaks was 1.2 outbreaks per 1 million population. Outbreaks were reported by 32 states; Washington, DC; and Puerto Rico. Hawaii (25.3 outbreaks per 1 million population), Puerto Rico (16.5), Florida (6.3), and Alaska (5.4) had the highest reported rates. A food source was identified in 396 (99%) outbreaks, of which 379 (96%) implicated fish. Among 313 outbreak investigations in which the food importation status was known, 219 (70%) of the implicated foods were not imported. Of the 377 outbreaks in which a single location of food preparation was identified, private homes were reported in 193 (51%) outbreaks and sit-down dining restaurants were reported in 130 (34%) outbreaks.Nearly all outbreak reports (95%) implicated scombroid toxin (192 outbreaks, 597 illnesses, and six hospitalizations) or ciguatoxin (189 outbreaks, 619 illnesses, and 67 hospitalizations). For the 192 scombroid toxin outbreaks, the jurisdictions reporting the highest number of outbreaks were New York (43 [22%]), Florida (38 [20%]), California (23 [12%]), and Hawaii (18 [9%]). Of the 189 scombroid toxin outbreak reports with a reported food source, the majority (76%) implicated tuna. Of the 131 scombroid toxin outbreak reports with information on importation status, 70 (53%) implicated imported foods. Of the 181 scombroid toxin outbreak reports with a single location of food preparation, sit-down dining restaurants were identified in 104 (57%) outbreaks.Of the 189 ciguatoxin outbreaks, Florida reported 88 (47%) outbreaks, Puerto Rico reported 55 (29%), and Hawaii reported 18 (10%). Of the 187 ciguatoxin outbreak reports with a reported food source, 58 (31%) implicated barracuda, 25 (13%) implicated grouper, and 22 (12%) implicated amberjack. The majority (87%) of the 164 ciguatoxin outbreak reports with a known importation status reported foods that were domestically caught. Of the 178 ciguatoxin outbreak reports with a single location of food preparation, private homes were identified in 142 (80%) outbreaks.Shellfish-associated toxins caused 13 outbreaks, including paralytic shellfish poisoning in six (46%) outbreaks, neurotoxic shellfish poisoning in four (31%) outbreaks, and amnesic shellfish poisoning, diarrhetic shellfish poisoning, and unknown shellfish poisoning each associated with one (8%) outbreak. These outbreaks resulted in 40 illnesses and nine hospitalizations. Florida reported five (38%) of these 13 outbreaks and Alaska reported four (31%). Of the 13 total shellfish-associated outbreaks, mussels were implicated in four outbreaks (31%), sea snails in four (31%), and clams in three (23%). None of these outbreak investigations implicated imported shellfish. Of the 11 shellfish-associated toxin outbreaks with a reported single food preparation location, private homes were identified in eight (73%) outbreaks.

Characterizing marine toxin outbreaks reported to FDOSS can guide opportunities for prevention. Scombroid toxin and ciguatoxin caused the most reported outbreaks, illnesses, and hospitalizations of all marine toxins, indicating they are important targets for public health intervention. More than half of scombroid toxin outbreaks were caused by imported fish and fish prepared in sit-down dining restaurants. Most ciguatoxin outbreaks were caused by reef fish, fish that were not imported, and fish prepared in private homes. Outbreaks attributed to shellfish-associated toxins were caused by shellfish that were not imported and were prepared in private homes. Outbreaks caused by ciguatoxin and those associated with shellfish-associated toxins were predominantly reported by jurisdictions where toxin-producing algal species are endemic and often implicated recreationally caught fish and shellfish. Geographic expansion, increasing frequency, and increasing intensity of harmful algal blooms in U.S. coastal waters might increase the presence of ciguatoxin and shellfish-associated toxins in aquatic animals. The varying characteristics of outbreaks caused by marine toxins highlight the need for tailored prevention measures that account for both environmental conditions and consumer behaviors.

The findings in this report can be used by public health practitioners to guide food safety prevention efforts and raise awareness about marine toxins and associated illnesses. Prevention of outbreaks resulting from scombroid toxin from both imported and domestic fish involves maintaining temperature control of seafood below 40°F (4.4°C) from catch to consumption. Understanding the needs and practices of recreational harvesters could help public health officials craft targeted communications about safer practices for harvest location and affected aquatic species. Reducing the harvesting of reef fish and shellfish from high-risk areas, especially during and immediately after harmful algal blooms, might prevent illnesses from these toxins.