A recent study from the Centers for Disease Control and Prevention (CDC) stated that marine toxins continue to be responsible for most of the noninfectious foodborne outbreaks that occur in the U.S. every year, and of the cases reported, nearly all are linked to two types: scombroid toxin and ciguatoxin.
Using data from the CDC’s Foodborne Disease Outbreak Surveillance System (FDOSS), the study analyzed 402 noninfectious foodborne disease outbreaks that occurred from 2011 to 2023 and led to 1,280 illnesses, 96 hospitalizations, and one death. The CDC explained that for an incident to be an outbreak, there must be two or more cases of a similar illness that are associated with a common food exposure.
Scombroid toxin is caused by a harmful buildup of histamine formed when bacteria multiply on fish that are not properly stored from catch to consumption. Once that histamine is formed, it cannot be destroyed through cooking, freezing, or canning and can cause food poisoning.
According to the study, among the 189 scombroid toxin outbreaks that occurred over the 12-year period with an identified food source, 76 percent implicated tuna as the culprit. Of the 131 outbreaks with known import status, 53 percent stemmed from imported foods, and among 181 outbreaks with a known preparation location, 57 percent were linked to sit-down dining restaurants.
Ciguatoxin, meanwhile, is a marine neurotoxin produced by algae that grow on tropical and subtropical reefs. The algae need surfaces to attach to, such as macroalgae, seagrass, or damaged coral. As a result, reef damage from hurricanes, runoff pollution, or coastal construction can create conditions for toxin-producing algae to thrive. The toxin then moves up the food chain from small fish to larger reef predators, concentrating in the flesh and potentially taking months or years to build to dangerous levels.
Of the 187 ciguatoxin outbreaks with an identified food source, 31 percent implicated barracuda, 13 percent involved grouper, and 12 percent involved amberjack. Among outbreaks with known import status, 87 percent involved domestically caught fish, and 80 percent of outbreaks with a known preparation location involved food prepared in private homes.
Other toxins that resulted in outbreaks included shellfish-associated toxins, which caused 13 outbreaks over the time frame covered, including paralytic shellfish poisoning and neurotoxic shellfish poisoning, among others. Mussels, sea snails, and clams were identified in the report as the cause of outbreaks.
No shellfish-associated toxin outbreaks with known import status involved imported shellfish, and 73 percent of the outbreaks with a known preparation location involved food prepared in private homes.
The jurisdictions with the highest outbreak rates were Hawai’i, Puerto Rico, Florida, and Alaska.
The CDC noted that certain parts of the seafood supply chain, including vessels that harvest or transport fish but do not otherwise process them, can be exempt from essential oversight, creating possible gaps in proper seafood handling before seafood reaches restaurants, retailers, or consumers.
The agency also highlighted that commercial shellfish testing and state shoreline monitoring have helped reduce commercial poisonings, but ciguatoxin is often linked to domestically caught reef fish prepared in private homes, making harvest advisories, fishing regulations, and public awareness especially important.
The CDC said these findings can help public health practitioners guide food-safety prevention efforts and raise awareness of these marine toxin risks, especially as warming waters, coral reef damage, and stronger storms make outbreaks of ciguatoxin and shellfish-associated toxins a growing concern.
