New analysis suggests that there are more than 25 times the amount of people in Florida than previously thought sickened by a rare, dangerous food-borne toxin carried by popular sport fish.

The toxin, ciguatera, is carried by fish such as barracuda, grouper, and amberjack and can cause severe nausea, vomiting and, occasionally, neurological symptoms. It is the most common type of fish-related food poisoning in the world.

The research, carried out by the University of Florida's Emerging Pathogens Institute and the Florida Department of Health, found that there are an estimated 5.6 cases per 100,000 people – much higher than the 0.2 per 100,000 that was derived from reports that physicians submit to the Department of Health.

Elizabeth Radke, the lead author of the study, published in the American Journal of Tropical Medicine and Hygiene, said: "The rate of illness was found to be higher than previously estimated. Areas around Miami and in the Florida Keys are particularly affected."

The team believe that the significantly lower figure was due to the fact that many people who got it did not see a physician, coupled with physicians not reporting a certain amount of cases to the public health board and doctors not recognising it as a condition separate to other food-borne illnesses.

The study found that Hispanics in the Florida area were worst affected by ciguatera poisoning, which it attributes to "cultural preferences for consumption of barracuda, which has been shown to have a high risk of containing ciguatoxins".

It calls for continued targeted public health outreach. Radke added: "I think there is a broader awareness the farther south you go that barracuda are carriers but perhaps not as much awareness that a fish like grouper or amberjack can carry ciguatera. I don't think that people necessarily need to stop eating these other fish but they need to be aware there is a risk, and if they start feeling sick after eating, they should see a physician."