Trends in dengue virus positivity & serotyping in Rajasthan

Background & objectives Dengue virus causes frequent outbreaks and epidemics with high morbidity and mortality. It is important to monitor the trends of the dengue virus and its serotypes. We carried out the present work to study the prevalence of the dengue virus and its serotypes in clinically suspected cases of dengue in Rajasthan. Methods A total of 1,47,777 individuals reporting as pyrexia of unknown origin or clinically suspected of dengue infection were included in this study. The presence of dengue NS1 antigen and dengue IgM was tested by ELISA. Nucleic acid extraction and PCR was done for detection of dengue virus RNA. Serotyping of representative dengue PCR-positive samples was done by real time PCR. Results Of the 1,47,777 dengue suspected cases, 28092 (19.01%) were positive for dengue by NS1antigen or IgM ELISA. Year-wise percentage positivity from 2015 to 2022 was 30.42, 16.49, 17.81, 20.15, 20.50, 9.25, 24.55 and 15.16 per cent, respectively. Males of age >15 yr were found to be more commonly affected. The number of dengue cases was significantly higher during the post-monsoon period throughout the eight-year study period. All four dengue serotypes circulated during the study period. DENV-2 and DENV-3 were the predominant serotypes during 2015 to 2017, while DENV-1 and DENV-2 were predominant during 2018 to 2022. Interpretation & conclusion The findings of this study suggest that the dengue positivity in Rajasthan was the highest in post-monsoon season among adult males. The serotype prevalent varied from time to time and was helpful in understanding the changing epidemiology of DENV.