RESUMO
Objective To isolate and identify the Dengue virus(DEN)from the sera of patients with unknown fever in summer and autumn in Dushan and Xingyi areas of Guizhou province,China.Methods From June 2005 to October 2005.356 blood samples were collected from patients with unknown fever in Dushan and Xingyi areas of Guizhou province.The serum samples were inoculated on the C6/36 cell monolayers.After three blind passages,the cytopathie effect(CPE)Was observed.Identification of DEN antigen was earried out by indirect immunofluorescence assay(IFA)with the monoclonal antibody(McAb)against DENl-4 virus.The total RNA was extracted from the serum and tested by RT-PCR with the universal primer for DEN NS region.And determination of the RNA sequenee Was performed,and phylogenetic analysis was carried out.Results Three serum samples caused CPE and were proved as DEN2 positive by IFA,RT-PCR and senquence determination.The phylogenetic tree analysis showed that the isolated virus strains had the closest relations with the systemic evolution of the strains DEN2-43 and DEN2-44.Conclusion DEN infections exist in the population of Dushan and Xingyi of Guizhou,China.