Crimean-Congo haemorrhagic fever virus: sequence analysis of the small RNA segments from a collection of viruses world wide.

Crimean-Congo haemorrhagic fever virus (CCHFv) is a member of the genus Nairovirus in the family Bunyaviridae. It possesses a tripartite, single stranded RNA genome of negative polarity consisting of large (L), medium (M) and small (S) segments. CCHF virus is enzootic in life stock and wild animals in many parts of the Middle East, Asia and Africa and is also recognised in Southeast Europe. Severe disease, manifest as haemorrhagic fever and high mortality rates (up to 50%), is only recognised in humans. We have determined the complete sequence of the small genomic RNA segment from several strains of CCHF virus from outbreaks in Pakistan 2000, Baghdad 1976 and Uzbekistan 1967. Phylogenetic analysis of three datasets of sequences from the small genomic RNA segment available from a range of strains indicates that they can be divided into seven subtypes. Superimposed on this pattern are links between distant geographic locations, pointing to the existence of a global reservoir of CCHFv. In some cases these links may originate from trade in livestock, and long-distance carriage of virus or infected ticks during bird migration.