Molecular Diversity of Dengue Virus Serotypes 1–4 during an Outbreak of Acute Dengue Virus Infection in Theni, India

Background: Dengue fever (DF) is caused by an arthropod-borne dengue virus (DENV), has four serotypes and several genotypes. Although having clinical and epidemiological significance, the information on the circulating serotypes/genotypes is scarce in India. Materials and Methods: Blood specimens were collected from the patients suspected of DF and they are tested for DENV NS1 antigen and DENV IgM by ELISA. Antigen-positive samples were further serotyped by reverse transcriptase polymerase chain reaction. Representative samples from each serotype were sequenced to identify the genotypes. Results: All the four DENV serotypes were detected with the pre-dominance of DENV-1 (n = 49; 41.9%). Cases with multiple DENV serotype infections were also identified. Genotyping showed that DENV-1 belonging to genotype I, DENV-2 cosmopolitan (IV), DENV-3 genotype III and DENV-4 genotype I were active in the circulation during the outbreak in 2017. Conclusion: Our study documents the molecular characteristics of DENV circulating in our geographical locality. The detection of heterologous DENV serotypes highlights the importance of regular molecular monitoring for the early recognition of any switch in pre-dominant serotype.