Vibrio parahaemolyticus is bacteria that has been isolated from sea water, shell fish, finish, plankton and salt springs. It has been a major cause of food poisoning in Japan and Japanese have done several studies on it. They have confirmed the presence of V. parahaemolyticus in the north and central Pacific with the highest abundance in the inshore waters, particularly in or near large harbors.

A man named Nishio studied the relationship between the chloride content of seasonal distribution of V. parahaemolyticu and concluded that while the isolation of V. parahaemolyticus was independent of the sodium chloride content, the distribution of V parahaemolyticus in sea water was dependent on the water temperature. In fact it has been isolated in high frequencies during summer, from June to September, but was not isolated with the same frequency in winter.

Within four or five days after eating contaminated foods, a person will begin to experience diarrhea, the most common symptom; this will very often be accompanied by stomach cramps, nausea, and vomiting. Headache and fever, with or without chills, may also be experienced.