Ancient common ancestry of Crimean-Congo hemorrhagic fever virus.

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne RNA virus responsible for outbreaks of severe hemorrhagic fever in humans. Although CCHF was first detected in the 1940s, high levels of genomic diversity argue against a recent origin. Here, Bayesian coalescent analyses were used to estimate the rate of evolution and relative age of the virus. A total of 43 S, 34 M, and 23 L segment sequences from samples collected between 1956 and 2005 were analyzed from across the broad geographic range of the virus. Using a relaxed molecular clock model, nucleotide substitutions were estimated to have occurred at a rate of 1.09x10(-4), 1.52x10(-4), and 0.58x10(-4) substitutions/site/year for the S, M, and L segments, respectively. The most recent common ancestor of the viruses existed approximately 3100-3500 years before present, or around 1500-1100 BC. Changes in agricultural practices and climate occurring near the time of the most recent common ancestor of CCHFV may have contributed to its emergence and spread.