RESUMO
In 1965 an epidemiological study was made in an agricultural area of Guatemala to establish the etiology of a disease affecting certain families. The involvement of the central nervous system gave the impression that the disease was encephalitis of undetermined etiology. A study was made of the characteristics of the area, and of the economic and social situation of the inhabitants, and an entomological survey was undertaken to identify vectors. An epidemiological investigation was made of each case, as was a clinical examination of each patient. A search was made also for other etiological agents, especially toxic agents. Blood samples from patients, contacts, and the general population, as well as post mortem material from those who had died from the disease, were examined. The persons afflicted were Indians living in the mountains and cultivating corn and wheat. Except for small wooded areas, most of the land is cultivated; part of the crop is sold and the remainder is kept for food. The water they drink comes from mountain springs, and there is no system of excreta or garbage disposal. Insects are not plentiful in the area. Between July and October 45 cases of the disease occurred and of these 20 died. Only 12 families were affected, but many members fell ill and died. Over 50
of the cases occurred among children under 10 years of age, and 75 percent among those under 20 years of
