Molecular Typing of Imported Dengue Virus (DENV) Isolates from Patients in the Far East of Russia

Background: Dengue remains the most rapidly spreading mosquito-borne viral infection in the world with 30-fold growth during the last 50 years and its expansion to new areas. Dengue virus transmissions are effected by urbanization and international travel. Detection, identification and quantitation of Dengue virus beyond its endemic regions during global warming are necessary to estimate an epidemiological risk. Methods: Dengue virus strains were isolated from blood samples of patients with unknown fever. To confirm clinical diagnosis both RTPCR and ELISA to detect IgM/IgG were used. Sequencing of RT-PCR products corresponding to C-prM, E and NS5 genes with subsequent phylogenetic analysis performed for molecular typing. Results: During 2012-14 Dengue fever imported cases were confirmed in blood samples of 13 from 95 patients with unknown fever (13,7%) in Khabarovsk, Primorye and Sakhalin regions of the Far East, Russia. Using permissive tissue culture Vero E6 and susceptible suckling mice five Dengue strains of 1 and 3 types have been isolated. RT-PCR with Dengue serotype-specific primers and phylogenetic analysis of nucleotide sequences of RT-PCR products corresponding to C-prM, E and NS5 genes revealed Dengue viruses 1, 2 and 3 types. Conclusions: For the first time in Russia Dengue fever imported cases were confirmed by means of RT-PCR, ELISA and virus isolation. Molecular typing revealed Dengue viruses 1, 2 and 3 types in blood sample of patients after their return from travel to subtropical endemic regions.