AN ARBOVIRUS CLINE ACROSS THE NORTHERN-HEMISPHERE

The mode and tempo of arbovirus evolution and dispersal can help to ex plain the dynamics of pandemics, viral outbreaks, and emerging viruses . By comparing nucleotide and deduced amino acid sequences of their en velope proteins, we describe the continuous distribution of the tick-h ome encephalitis (TEE) complex viruses, the most important flaviviruse s in Europe, across major geographical areas and the conditions under which mutations occur. The analyses reveal a correlation between the g eographical and genetic distances of these viruses. The arthropod host appears to be a key factor for the formation and maintenance of this dine by constraining TEE dispersal and evolution. This is also illustr ated by comparisons with mosquito-borne flaviviruses. (C) 1995 Academi c Press, Inc.