Unravelling ecological factors influencing phylodynamics of Kyasanur Forest Disease in India.

Kyasanur Forest Disease Virus (KFDV) is a tick-borne flavivirus endemic to the Western Ghats region of India, with increasing reports of geographic expansion. This study employs phylogenetic analysis and spatial diffusion modeling to understand the evolutionary dynamics and transmission patterns of KFDV. Whole genome and E-gene sequences were analysed to identify major phylogenetic clusters, transmission velocity, and environmental factors influencing viral spread. The analysis revealed two primary phylogenetic clusters: Cluster A, originating in Karnataka, and linked to initial outbreaks (1957-1972) and subsequent re-emergence post-2010 in Karnataka, Kerala, and Goa; and Cluster B, which expanded from Maharashtra in the late 1970s into Tamil Nadu, Karnataka, and Kerala. Phylogenetic findings indicated a slow mutation rate, indicative of long-term viral persistence in sylvatic reservoirs rather than sustained human-human transmission. Spatial diffusion analysis estimated a median transmission velocity of 59.67 km/year. Environmental factors such as deforestation, land cover change, and livestock density acted as facilitators of viral spread, while urbanization, open water bodies, and precipitation served as resistance factors. The findings underscore the need for enhanced surveillance, ecological monitoring, and public health interventions to mitigate the increasing risk of KFD outbreaks. This study provides a comprehensive framework for understanding KFDV transmission and evolution, integrating phylogenetic and ecological data to improve risk assessment and guide control strategies in both endemic and emerging regions.