Remember 1897?

You are on a cruise ship well-known for its crazy seafood buffets. When passengers start getting sick, a call for, "Is there a doctor on board?" rouses you. Alas, you seem to be working every vacation. At first, you think this is just a viral GI bug because the passengers complain of diarrhea and abdominal cramps. But what's more remarkable is that this is followed by headache, memory loss, and disorientation. In severe cases, you note diminished reflexes, ophthalmoplegia, coma. One person is sent to shore because he needs an intensive care unit.

Challenge: What's the cause of this?

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