Kyasanur Forest Disease in India: Epidemiology, Transmission Ecology, Clinical Spectrum, Diagnostics and One Health Control

Abstract

Background: This narrative review synthesizes current evidence on Kyasanur Forest                     Disease (KFD), a tick-borne viral hemorrhagic fever endemic to India. Caused by Kyasanur Forest disease virus (KFDV), a member of the tick-borne encephalitis virus serocomplex, KFD                    represents an emerging zoonotic threat with expanding geographic distribution across the Western Ghats. Methods: A comprehensive literature review was conducted using PubMed, Web of Science, and Scopus databases, covering publications from 1957 to 2024. Peer-reviewed original studies, surveillance reports, and relevant reviews were included and synthesized narratively to integrate evidence on epidemiology, transmission ecology, pathophysiology, clinical spectrum, diagnostics, and prevention strategies. Results: In humans, KFD typically manifests after a 3–8-day incubation period with acute febrile illness, headache, myalgia, and severe prostration. Approximately 20% of patients develop a biphasic illness, with a subset progressing to neurological involvement during the second phase. The overall reported case fatality rate ranges from 3–5%. Diagnosis relies primarily on serological assays (IgM/IgG ELISA) and molecular detection by RT-PCR during early illness. Ecologically, KFDV circulates through enzootic cycles involving Haemaphysalis ticks and multiple vertebrate hosts, with monkey epizootics serving as sentinel indicators of local transmission. Geographic expansion has been associated with ecological disruption, deforestation, and increased human–tick interactions. Conclusions: Kyasanur Forest Disease remains an evolving zoonotic challenge driven by environmental change and complex transmission dynamics. Effective control requires strengthened One Health–oriented surveillance, improved vaccination coverage, and integration of viral genomic monitoring with clinical and ecological data to support early detection and targeted prevention.