Men and Women of all ages, excluding infants, became victims and cats
in victim's families often showed similar symptoms. Thus fish- and
shellfish- mediated food poisoning was first to become suspect.
Taking into consideration the geographical and chronological distribution
of the victims, it was surmised that a chemical substance contained in the
waste discharge from an acetaldehyde plant located on the shores of Minamata
Bay was causative agent. Mercury was not suspected at the beginning, and it
took there years for mercury theory to be formulated. This was due to the
peculiar etiology of this disease.