This volume summarizes selected papers presented at two symposia convened in the fall of 1989. The papers include information on the molecular biology, antigenicity, diagnosis, epidemiology, clinical aspects, pathogenesis, vaccines and other aspects of haermorrhagic fever with renal syndrome and tick (tick-borne encephalitis, Congo-Crimean haemorrhagic fever, Duqbe, orbiviruses, orthomyxoviruses) and mosquito-borne (California serogroup, alphaviruses from Mongolia, sandfly fevers in Central Asia and Afghanistan) viruses. Although covering a wide range of subjects and perspectives, the book is intended to provide readers with an integrated view of the geographical distribution, properties and effects, recognition and prevention of infections with these and other viruses. Included are papers describing newly recognized viruses, virus diseases, foci, techniques for detection and diagnosis, and vaccines.