According to the Regional Health Agency, Indian Ocean, the victims were affected by the tetrodotoxin in the pufferfish, a neurotoxin which causes increasing paralysis while the victim remains conscious and can be fatal. The mortality rate from acute tetrodotoxin poisoning is reportedly about 60 percent.
Pufferfish are strictly regulated in most countries and banned in others, and those who prepare dishes made from the fish are specially trained and licensed. There are several types of pufferfish, and each produces a different concentration of the neurotoxin.
According to the French Agency for Marine Research and Development, 23 tetrodotoxin poisonings have occurred in the Réunion area from eating pufferfish, the most recent in 1989. Of those 23 victims, 12 were hospitalized and two died.