RESUMEN
<p><b>BACKGROUND</b>To study the molecular biology of Xinjiang hemorrhagic fever (XHF) viruses, to explore its relationship with other Crimean-Congo hemorrhagic fever viruses, analyzing the epidemic origin and the tendency of geographic distribution of XHF.</p><p><b>METHODS</b>The S partial segment from the patient and tick samples collected in 2001 and 2002 was tested by RT-PCR, the positive samples were sequenced directly. The nucleotide homology of S partial segment as well as the whole segments were analyzed and the phylogenetic tree of S and M gene segments was drawn by computer.</p><p><b>RESULTS</b>All compared sequences of S partial segments from the patient and tick samples showed a high homology of nucleotide sequences. Phylogenetic tree divided all the analyzed viruses into three groups; Europe, African and Asian group. The Asian group can be divided further into another two branches: the middle Asian branch and the Chinese branch. All the Chinese isolates were clustered into one single group and was easy to be discriminated from the other isolates. The dividing of M segments seemed not completely related to the geographic origin of the viruses.</p><p><b>CONCLUSION</b>M segment classification was not consistent to the geographic distribution of the viruses. S segments analysis showed the close relationship of genetic background between the patient isolates and the tick isolates. Besides, all the Chinese isolates have the common evolution route and the gene structure characteristics displayed the regional distribution pattern.</p>