Pathogenicity and virulence of Kyasanur Forest disease: A comprehensive review of an expanding zoonotic threat in southwestern India.

Kyasanur Forest Disease (KFD) is a tick-borne viral hemorrhagic fever caused by the KFD virus (KFDV). First identified in 1957 in Karnataka, India, KFD primarily affects humans and non-human primates. The disease has a broad clinical manifestation, ranging from asymptomatic infections to severe hemorrhagic complications, with a mortality rate of 3-10%. Over time, KFD has shown a gradual geographical expansion, with cases now reported beyond Karnataka. KFD has been a public health challenge for nearly seven decades, as no effective vaccine or antivirals are available. Although humoral immunity is critical in controlling KFD infection, with neutralizing antibodies conferring durable protection, the role of cellular immunity is not well studied. Preventive strategies - such as tick control, community education, and well-planned surveillance - are vital to reducing disease burden. This review synthesizes knowledge on KFD, encompassing its discovery, epidemiology, clinical presentations, diagnostic assays, viral evolution, pathophysiology, immune mechanisms, interventions, and research priorities.