Molecular characterization of dengue viruses during an outbreak in Kolkata: A hospital-based study

Abstract

Context: Dengue, a mosquito-borne viral infection in the tropical regions of the world, has recently become a major public health concern. In West Bengal, several outbreaks of dengue fever occurred in the past few years. In the present study, serological analysis, molecular detection, and serotyping of dengue virus were done to identify the serotype/s presently circulating in the region. Methods: The present study was conducted for a period of 1 year from November 2017 to October 2018 in the Department of Microbiology, ID and BG Hospital, Kolkata. 5240 blood samples collected from clinically suspected dengue fever cases were screened for dengue specific immunoglobulin M (IgM) antibody by MAC-ELISA and NS1 antigen by NS1 ELISA according to the duration of fever as per the National Vector Borne Disease Control Program guidelines. Molecular detection and serotyping were done in 70 NS1 positive samples by nested reverse transcription-polymerase chain reaction. Results: Total 5240 samples were tested for dengue. About 30.48% (1597) were serologically reactive for dengue infection (either IgM or NS1). Among these, 80.52% (1286) were NS1 reactive and 19.47% (311) were IgM reactive. Male predominance (66.37%) was observed throughout the study period. A post monsoon season peak was also noted in our study. DEN2 was found as most prevalent serotype presently circulating in the region. Conclusions: Laboratory-based active surveillance system is required which can forecast dengue epidemics by detecting increasing number of dengue cases or changing pattern in the prevalent serotype as a specific serotype (viz.DEN2) is associated with higher incidence of complications. This will help alert the public and physicians to diagnose properly and treat cautiously the complicated dengue cases.