Epidemiological Trends and Patterns of Scrub Typhus in India: A Retrospective Analysis Based on Integrated Disease Surveillance Programme (IDSP) Data (2009-2018)

Abstract Background: Scrub typhus, a vector-borne febrile illness caused by Orientia tsutsugamushi , has shown significant global resurgence, affecting an estimated one billion people at risk and causing up to one million cases annually. In India, it is a major cause of acute undifferentiated fever but remains under-recognized and a clear research gap regarding long-term national trends, and the heterogeneity of case fatality across states exists. This study aimed to quantify the national burden, geographical distribution, temporal trends, and mortality associated with scrub typhus using Integrated Disease Surveillance Programme (IDSP) data, identifying surveillance and reporting gaps. Materials and Methods: A retrospective, trend-based analysis was conducted using data from the IDSP portal covering 2009–2018. Data were extracted into Microsoft Excel and analyzed using SPSS version 20 and Epitools (version 2023.2). The Chi-square test for linear trend assessed temporal changes in the case fatality rate (CFR). Results: A total of 1,141 cases and 39 deaths were reported across 16 states/UTs, yielding an overall CFR of 3.4%. A significant decline in CFR was observed over the decade ( P < 0.001). Northeast India, particularly Mizoram (503 cases) and Meghalaya (136 cases), contributed the highest caseloads. High fatality rates in low-case states (e.g. Gujarat CFR 100%; Rajasthan CFR 74.1%) likely reflect reporting bias or data quality issues. Conclusions: Scrub typhus shows a nationwide spread with seasonal peaks from October to January. Strengthened surveillance, early diagnosis, and public awareness are essential to reduce mortality and ensure standardized data reporting.