Field based Epidemiological Survey of Kyasanur Forest Disease Cases During the 2018–2020 Outbreak

Abstract

Kyasanur Forest Disease (KFD) is a tick-borne viral hemorrhagic fever endemic to the Western Ghats of India. In recent years, the disease has shown an expanding geographic distribution, raising public health concerns. A field-based epidemiological survey was conducted during the 2018-19 and 2019-20 KFD outbreaks across the districts of Shivamogga, Chikkamagaluru, and Uttara Kannada in Karnataka. Data on confirmed cases, vaccination status, mortality, and behavioral risk factors were collected and analyzed. The 2018-19 outbreak in Aralagodu village, Sagar Taluk, resulted in 20 deaths and established the area as a new KFD hotspot. During 2019-20, newer regions such as N. R. Pura and Siddapura Taluks reported 60 confirmed cases. Despite ongoing vaccination programs (prior to their suspension in 2020), several breakthrough infections occurred among individuals who had received two or more doses, indicating limited vaccine-induced immunity. However, vaccinated individuals generally experienced milder disease, while unvaccinated patients presented with severe hemorrhagic and neurological symptoms. Behavioral exposure, particularly forest visits for collecting leaf litter and firewood, emerged as a key risk factor. Additionally, displacement of infected bonnet macaque troops was observed, suggesting a possible ecological driver of viral spread. The findings highlight the persistent challenges in KFD control, emphasizing the need for a more effective vaccine, strengthened public awareness initiatives, and integrated ecological surveillance to mitigate future outbreaks and limit the disease’s spread to new regions.