GEOGRAPHIC-DISTRIBUTION AND EVOLUTION OF ROSS RIVER VIRUS IN AUSTRALIA AND THE PACIFIC ISLANDS

We examined the molecular epidemiology and evolution of Ross River (RR ) virus in Australia and the pacific Islands. Nucleotide sequences of the E2 and E3 genes of five RR virus strains revealed remarkable conse rvation between 1959 and 1989 with a maximum divergence of only 3.3%. Sequence data from a 505-base pair fragment of the E2 gene from 51 add itional strains showed that RR virus has diverged genetically into thr ee separate groups although at least 95% sequence homology was still m aintained between all 56 strains. Each genetic type predominates in a particular geographic region of Australia and can be broadly defined a s occurring in the western, northeastern, and southeastern regions of Australia. However, some RR virus strains did not follow this pattern of geographic distribution indicating movement of virus by the travel of viremic humans or livestock across the continent The Pacific Island s isolates all belong to the southeastern genotype. These findings sug gest genetic divergence and independent evolution of RR virus within g eographically isolated enzootic fool; however, selective pressures mai ntain high nucleotide conservation in nature. (C) 1995 academic Press, Inc.