Tetrodotoxin-associated snail poisoning in Zhoushan: a 25-year retrospective analysis.

Outbreaks of paralytic snail poisoning have recently occurred in Asia, especially in China. The epidemiological characteristics of this disease from an outbreak in Zhoushan City, China, were recorded. Forty-two outbreaks of paralytic snail poisoning, involving 309 cases of illness, occurred from 1977 to 2001. Sixteen people (5.2%) died, 48 people (15.5%) required intubations, and 140 people (45.3%) required emergency hospital treatment as a result of these outbreaks. Outbreaks involved multiple marine snail species and occurred primarily during the summer (from June to August) on 11 islands with high population densities. Peak numbers of outbreaks and amounts of snail toxicity occurred from 1978 to 1979, from 1985 to 1987, and from 1992 to 1994. Toxicity varied depending on specimen, region, and season. The toxin involved was identified as tetrodotoxin. The data obtained in this study suggest that snails should not be eaten unless they are certified to be nontoxic.