A family of four suffered the neurological symptoms of paralytic shellfish poisoning after eating mussels. The epidemiologist investigated and identified no additional ill persons. This had been the first instance of paralytic shellfish poisoning reported in Maine in thirty years. Paralytic shellfish poisoning is caused by Saxitoxin. Saxitoxin is one of the most potent natural toxins known. Shellfish become contaminated during toxic algal blooms.