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 1.09 × 10−4, 1.52 × 10−4, and 0.58 × 10−4 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.