Kuru is apparently determined by a dominant gene with incomplete expressivity producing fatal disease in childhood in homozygotes of both sexes and in adult life in heterozygous female carriers, but not usually penetrant in male carriers. This simplest genetic hypothesis which will account for the unprecedented situation which kuru presents in New Guinea has not yet been refuted by studies of genealogies in the kuru region or by other human ecological investigations. No outsiders have yet developed kuru on residence in the region. Carriers of the kuru gene must possess a distinct genetic advantage in the region, for unless such carriers were genetically more fit than non-carriers loss of the gene in nonreproducing homozygotes would have prevented its attaining its present high frequency in the society.
The restricted marriage pattern with island-like isolation of small marriage pools would have led to extremely slow diffusion of a new mutant kuru gene throughout the population unless the mutation was present originally in the progenitors of an Urstamm from which at least the central subgroups of the current kuru afflicted population were derived before the near-total marriage isolation of the various groups of hamlets developed.
Environmental variables and the possibilities of infectious, toxic or deficiency factors operating alone or with genetic dependence have not yet been fully excluded. However, the principal investigative approach is the biochemical investigation of intermediary metabolism of kuru patients and normal natives of the kuru region, some destined to die of kuru. Such studies should advance our understanding of kuru etiology and pathogenesis whether or not it is a solely genetically mediated disease.
The problems and methods of epidemiological work in the region are discussed and the ethnic setting of kuru further elaborated. A summary of the age and sex distribution of 804 studied kuru cases is given.