Epidemiology of Kyasanur forest disease in India, 2000-2025: a systematic review and meta-analysis

Kyasanur forest disease (KFD) is a tick-borne viral haemorrhagic fever that has recently expanded beyond its historically endemic focus in Shimoga district, Karnataka, India. Robust estimates of disease burden, distribution and clinical manifestations remain limited. This systematic review and meta-analysis aimed to estimate pooled KFD positivity, case-fatality rates and to characterise the distribution and clinical features of KFD across India.

Four databases including PubMed, Scopus, Web of Science, Embase along with grey literature (Google Scholar) were searched (January 1, 2000-January 15, 2025). Non-English publications, studies published prior to 2000, reviews, systematic reviews, meta-analyses, seropositivity assessments, and investigations restricted to diagnostic test comparisons were excluded. Eligible studies included those evaluating KFD diagnostic positivity among clinically suspected patients, tick and non-human primate infectivity, outbreak investigations, symptoms, and mortality. Following duplicate removal, study quality was verified utilising NIH Quality Assessment Tool, resulting in exclusion of poor-quality papers. Primary outcomes, diagnostic positivity among clinically suspected KFD patients and case fatality ratio (CFR), were pooled using random-effects meta-analysis with logit transformation. PROSPERO registration: CRD42024621971.

Of the records screened, 31 studies met the inclusion criteria. Meta-analysis of 18 studies included 7907 suspected patients with 1431 individuals tested positive, yielding a 21% pooled diagnostic positivity rate (95% CI: 14-30). Positivity varied substantially by district. Of 2798 cumulative cases, specific gender details were available for 1422, comprising 738 females and 684 males. The pooled CFR was 4% (95% CI: 2-8). KFDV circulation in ticks was reported in 11 studies (3466 tick pools tested, 116 positive), predominantly Haemaphysalis spinigera and Haemaphysalis turturis. Fever, myalgia and headache were the most consistently reported symptoms.

KFD has spread significantly from its initial origin to neighbouring states, and intensifying surveillance of new foci is critical. Monkeys appear to seed new foci for KFD, while ticks are responsible for sustaining transmission. Early diagnosis and case management can significantly improve patient outcomes.

None.