Walsh & Hoyt: Epidemiology

Viliuisk encephalomyelitis is confined to the Iakut population that lives along the Viliui River in Siberia. Initial cases occurred in the Middle Viliui area, and the disease subsequently spread to the adjacent Upper and Lower Viliui areas as migration in these directions increased. The disease eventually reached the Lena-Aldan Valley, a more highly populated region along the river. Although VE may begin in any season, most cases are recorded in May, June, and July, when outdoor activities are frequent. Most patients are between 30 and 50 years old when they develop the initial manifestations of the disease, with the average age being 35 years for men and 40 years for women. Nevertheless, the disease may begin as early as the second decade of life or as late as the seventh. Men and women are equally affected.