Long-Term Epidemiological Trends, Seasonal Dynamics and Spatial Heterogeneity of Scrub Typhus in Kerala, India: A Surveillance-Based Analysis (2012–2024)

Abstract

Scrub typhus, caused by Orientia tsutsugamushi, is a major cause of acute undifferentiated febrile illness in South India. This study describes the epidemiological, seasonal, and spatial trends of scrub typhus in Kerala from 2012 to 2024 using secondary surveillance data. A total of 6,824 confirmed cases and 127 deaths were reported during the study period, yielding an overall case fatality rate of 1.86%. Disease incidence showed marked temporal fluctuations, with major peaks in 2015, 2022, and 2024, indicating persistent endemic transmission with periodic outbreaks. Seasonal analysis revealed a highly significant variation in case occurrence (χ² = 1070.5, df = 2, p < 0.001), with the highest burden during winter (47.9%) followed by the monsoon season (36.2%). Spatial analysis demonstrated pronounced geographic heterogeneity, with Trivandrum district contributing over 70% of reported cases. The findings underscore the continuing public health importance of scrub typhus in Kerala and highlight the need for strengthened surveillance, early diagnosis, and targeted district-specific control strategies.