Prevalence and risk factors of scrub typhus infection: Findings from a cross-sectional study in a rural setting in southern Tamil Nadu, India

<h2>Abstract</h2><h3>Problem considered</h3> Scrub typhus is a significant yet underdiagnosed cause of acute febrile illness in rural areas, where limited diagnostics and overlapping symptoms hinder timely detection. Existing evidence is largely hospital-based, with minimal data from community settings. This study aimed to estimate the prevalence and identify risk factors for scrub typhus using serological and molecular diagnostics in a rural population of southern Tamil Nadu. <h3>Methods</h3> A cross-sectional study was conducted between October 2022 and September 2024 at the Upgraded Primary Health Centre, Kallur, Tirunelveli. A total of 231 adults with fever ≥38°C lasting more than five days were enrolled. Scrub typhus diagnosis was based on IgM ELISA (OD ≥1.50), Weil-Felix test (OXK titre ≥1:80), and quantitative real-time PCR (qRT-PCR) targeting the 47-kDa <i>htrA</i> gene. Multivariable logistic regression was used to calculate adjusted odds ratios (aOR) with 95% confidence intervals (CI) to identify independent risk factors. <h3>Results</h3> Scrub typhus was confirmed in 24 of 231 patients (10.4%). Of these, 8 were positive by both Weil-Felix and IgM ELISA, 10 by IgM ELISA alone, and 6 exclusively by qRT-PCR. Molecular testing identified 25% of cases missed by serology. Significant risk factors included close animal contact (aOR: 2.48, 95% CI: 1.01 - 6.09) and residence near bushy or scrub vegetation (aOR: 2.75, 95% CI: 1.02 - 7.38). <h3>Conclusion</h3> Complementary testing with serological and qRT-PCR can improve early detection of scrub typhus. Public health interventions at the community level should focus on behavioural and environmental risk factors by strengthening health education and surveillance.