Family clustering of Viliuisk encephalomyelitis in traditional and new geographic regions

Abstract

Viliuisk encephalomyelitis is an acute, often fatal, meningoencephalitis that tends to develop into a prolonged chronically progressive panencephalitis. Clinical, neuropathologic, and epidemiologic data argue for an infectious cause, although multiple attempts at pathogen isolation have been unsuccessful. To assess mechanisms of disease transmission and spread, we studied 6 multiplex families. Secondary cases occurred among genetically related and unrelated persons in a setting of prolonged intrahousehold contact with a patient manifesting the disease. Transmission to unrelated persons was documented in a densely populated region around the city of Yakutsk in which Viliuisk encephalomyelitis had not been previously known. Initially identified in a small Yakut-Evenk population on the Viliui River of eastern Siberia, the disease subsequently spread through human contacts to new geographic areas, thus characterizing Viliuisk encephalomyelitis as an emerging infectious disease.

Figure

Location of families with Viliuisk encephalomyelitis characterized in this report. Arrow indicates the general direction of Viliuisk encephalomyelitis dispersion from traditional disease-endemic areas on the Viliui River to densely populated regions of the Sakha (Yakut) Republic around the capital city of Yakutsk.