Imported cases of dengue fever in Russia during 2010–2013

ObjectiveTo confirm dengue infection among Russian tourists returned from Southeast and Mexico in 2010–2013 with clinical signs of infection.MethodsBlood and serum samples from patients were collected. NS1 antigen and human IgM/IgG antibodies to dengue virus were identified using commercial tests manufactured by “Standard Diagnostics, INC.”, Korea. ELISA test was used for the quantitative analyses of human IgM/IgG antibodies to dengue virus (“Orgenics Ltd.”, Israel). Viral RNA was detected using commercial real–time PCR tests manufactured by “Genome Diagnostics Pvt. Ltd.”, India and “Vector”, Russia. Genotypes of revealed dengue viruses were determined employing nucleotide sequencing and phylogenetic analysis of 5′–UTR of the viral genome.ResultsA total of 98 collected blood samples were analyzed. Fifty samples were positive for at least one of four markers of dengue infection. IgM to dengue virus were revealed in 38 samples, in 25 samples IgM were combined with IgG. NS1 antigen was detected in 43 samples. 22 serum samples were positive for dengue virus RNA. The majority of samples (12 patients) from tourists returned from Thailand were positive for genotype 1 of dengue virus, 2nd and 4th genotype were identified each in 1 patient.ConclusionsDue to laboratory confirmed cases of imported dengue fever in Russia, the differential diagnosis of dengue is strictly recommended for tourists returning from endemic areas.