As the small motorboat chugs to a halt, three travellers, wind-beaten from the three-hour journey along the Atrato river, step on to the muddy banks of Bellavista, an otherwise inaccessible town in the heart of the heavily forested north-west of Colombia. They swing their hessian bags – stuffed with bedsheets, dried beans and cuddly toys – to their shoulders and clamber up a dusty path. Tucked inside the bag of one of the travellers, neuropsychologist Sonia Moreno, is the reason they are here: a wad of unfinished, hand-drawn charts of family trees.
The people whose names are circled on the charts have Huntington’s disease, an incurable genetic brain disorder that usually starts between the ages of 35 and 45 years. It begins with personality changes that can make them aggressive, violent, uninhibited, anxious and depressed. The disease…