Molecular Analysis of Dengue Virus Serotypes Circulating in Chennai, Tamil Nadu, India

Introduction: Dengue fever is one of the most important arboviral infections all over the world. Globally, 50% of the human population is at risk of dengue virus infection. Circulation of more than one serotype and virulent genotypes are responsible for major outbreak with high mortality in any geographical region. Aim: To identify the Dengue virus serotypes and genotypes circulating in Chennai, Tamil Nadu, India. Materials and Methods: Dengue serum samples were subjected to Reverse Transcriptase-PCR and representative samples were sequenced, subsequently; Maximum-Likelihood phylogenetic tree was constructed by MEGA 7 software. Results: Out of 140 samples tested, 45 were positive for different serotypes of dengue virus. Among the 45 PCR positives, 12 (26.7%) and 5 (11.1%) samples were positive for Dengue virus-2 and Dengue virus-3 respectively. The remaining 28 (62.2%) samples showed more than one serotype infection. The following combinations of multiple infections were observed in the present study: one sample (2.2%) had mixed infection of Dengue virus-1, 2; seven samples (15.5%) had mixed infection of Dengue virus-2, 3; 10 samples (22.2%) had mixed infection of Dengue virus-1, 2, 3; three samples (6.7%) had mixed infection of Dengue virus-2, 3, 4 and seven samples (15.6%) had mixed infection of all four serotypes. The predominant serotypes were Dengue virus-2 and 3 when multiple serotypes were concerned. Genotyping analysis revealed that Dengue virus-1 sequence belonged to Genotype-I, Dengue virus-2 belonged to Genotype-IV, Dengue virus-3 belonged to Genotype III. Conclusion: In the present study, authors conclude that the circulation of multiple serotypes with a high number of concurrent infections, re-emergence and continuous circulation of genotypes in our region. The burden of dengue viral disease in India is massively under-reported. Hence detailed continuous molecular surveillance studies and stringent control measures are urgently warranted to save lives from dengue-related mortalities.