Viral Evolution
This virus was first identified in Tanzania in the 1953 appears to have evolved from an alphavirus ~1713 AD (95% credible interval: 1573 - 1843) in Africa. The East/Central/South African (ECSA) and Asian strains diverged within the last 150 years (95% HPD: 1879 to 1927). The extant ECSA strains - which include the first isolate of this virus - evolved between 1924 and 1943.
The Asian group split into two clades: an Indian lineage which has probably become extinct and a Southeast Asian lineage. The Southeast Asian lineage spread from Thailand to Indonesia; and then to the Philippines and more recently Malaysia. The recent Indian Ocean basin outbreak that began in 2004 appears to have originated from the ECSA group back in 2002 (95% credible interval: December 2001 to December 2003).
The estimated overall mutation rate is 4.33 × 10−4 nucleotide substitutions per site per year - a rate similar to those forun in other viruses with RNA genomes.
Read more about this topic: Chikungunya
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