Let me start by clarifying that people do not "get" synesthesia like they can get a cold or a disease. Synesthesia is a neurological condition that one is born with. In some instances, head trauma can cause synesthesia to be 'gained' in people who previously did not have it. By and large, though, synesthesia is something one has from birth. It is a trait - not a disease- that tends to run in families.