Epidemiological and clinical characterization of dengue virus serotypes during 2017-2019 in southern Kerala, India

Background In the context of the largest dengue outbreak in the state of Kerala, India in 2017, along with global evidence of changing epidemiology of dengue virus and its distribution, this study was planned to understand the epidemiological pattern of dengue infection and contemplate the clinical presentations of different serotypes. Methods This cross-sectional study was conducted in the Thiruvananthapuram and Kollam districts of Kerala, India, spanning 3 y from 2017 to 2019. We recruited adult patients based on the World Health Organization case definition of probable dengue fever to study their virological, spatial and clinical characteristics. Results Dengue infection was identified in 113 (33.9%) of the 333 probable dengue patients recruited. Dengue virus 1 (DENV1), along with its combinations (59.09%), was the predominant serotype during 2017, followed by DENV2. There was a marked increase in the proportion of DENV4 cases (34.56%) and concurrent infections (26%) in 2019. DENV3 infections were more likely to present with warning signs (adjusted relative risk 6.14 [95% confidence interval 1.3 to 29.4]) and a significantly lower platelet count (p=0.02). Conclusions The results highlight the hyperendemicity of dengue infection in the state and the changing pattern of dengue virus predominance along with redominance. The rise in DENV4 and concurrent infections put forth the possibility of a more severe future outbreak.