Surveillance for food poisoning of unknown origin derived from fresh seafood in Japan in 2009

Objectives The frequency of food poisoning from fresh seafood in Japan in 2009 and the regional characteristics and causative factors of such poisoning require investigation. In all cases, no bacterial or viral pathogens have been detected, although sliced raw flounder (sashimi) was suspected as being causative by the food sanitation inspectors. However, the cause of these poisonings is still unknown, and comprehensive approaches are required to completely understand the problem. Methods In order to obtain information on these poisonings, we sent a questionnaire to all 136 autonomies in Japan. It was found that many patients had contracted such poisoning. Symptoms included vomiting/nausea, diarrhea, and abdominal pain. Symptoms generally began within 12 hours of eating fresh seafood and resolved by the next day. The period of this survey was from January 1, 2009 to December 31, 2009. We analyzed the data by year and month and investigated the regional incidence. Results The response rate was 72.8% (99/136). Seventy autonomies answered “yes” and the remaining 29 answered “no.” There were 57 cases of definite and 171 cases of suspected food poisoning. Since 2003, the number of poisonings has increased annually, and they occur throughout the year, although they are most common in September in all autonomies. The highest incidence (53.9%) was reported for August, September, October, and November. Conclusion Food poisoning of unknown origin from fresh seafood in Japan shows seasonal characteristics, being more common during the hot seasons than in the cold seasons. When a pathogenic substance is not discovered, it is very difficult to confirm food poisoning, which is why the number of suspected cases was 3 times that of the confirmed.