genetic diversity of crimean congo hemorrhagic fever virus strains from iran

background: crimean congo hemorrhagic fever virus (cchfv) is a member of the bunyaviridae family and nairovirus genus. it has a negative-sense, single stranded rna genome approximately 19.2 kb, containing the small, medium, and large segments. cchfvs are relatively divergent in their genome sequence and grouped in seven distinct clades based on s-segment sequence analysis and six clades based on m-segment sequences. our aim was to obtain new insights into the molecular epidemiology of cchfv in iran. methods: we analyzed partial and complete nucleotide sequences of the s and m segments derived from 50 iranian patients. the extracted rna was amplified using one-step rt-pcr and then sequenced. the sequences were ana­lyzed using mega5 software. results: phylogenetic analysis of partial s segment sequences demonstrated that clade iv-(asia 1), clade iv-(asia 2) and clade v-(europe) accounted for 80 %, 4 % and 14 % of the circulating genomic variants of cchfv in iran respectively. however, one of the iranian strains (iran-kerman/22) was associated with none of other sequences and formed a new clade (vii). the phylogenetic analysis of complete s-segment nucleotide sequences from selected ira­nian cchfv strains complemented with representative strains from genbank revealed similar topology as partial sequences with eight major clusters. a partial m segment phylogeny positioned the iranian strains in either associa­tion with clade iii (asia-africa) or clade v (europe). conclusion: the phylogenetic analysis revealed subtle links between distant geographic locations, which we pro­pose might originate either from international livestock trade or from long-distance carriage of cchfv by infected ticks via bird migration.