Scrub typhus (ST) is an endemic disease caused by the bacterium Orientia tsutsugamushi in Southeast Asia, with 1 million cases annually, most commonly seen in countries such as India, Thailand, Korea, Australia, Russia, the Pacific Islands, and Japan[1]. A systematic review and meta-analysis by Dasgupta et al. (2024) found that the overall global pooled prevalence among the ST IgM-positive population was 57 % when combining urban and rural settings and 33 % when focusing solely on rural areas[2]. The Indian subcontinent, known for its rich ecological diversity, has reported cases of ST in nearly every state, highlighting it as a major health issue[3]. ST is clinically similar to other endemic acute febrile illnesses (AFI) such as dengue, leptospirosis, and typhoid fever[1]. Therefore, diagnosis depends more on laboratory tests than on clinical evaluations alone.

The Department of Health Research – Indian Council of Medical Research (DHR-ICMR) has established guidelines for diagnosing and managing rickettsial diseases in India. According to these guidelines, although the Micro-Immunofluorescence assay (IFA) is regarded as the “serological gold standard” because of its accuracy, but its high cost, the requirement for specialized technical skills and suboptimal performance lead to a recommendation for Enzyme-linked immunosorbent assay (ELISA) as the preferred diagnostic method[4,5]. Conversely, a molecular approach like polymerase chain reaction (PCR) provides higher specificity and sensitivity for diagnosing diseases. Nonetheless, the genetic variability among O. tsutsugamushi strains presents a major challenge when using genetic markers for PCR-based diagnosis. So far, >20 antigenically unique strains have been identified, including Karp, Kato, and Gilliam[1]. ELISA-based assays have emerged as preferred tests in recent times, as they are standardized and relatively less cumbersome to perform. In this study, we assessed the performance of the novel Scrub typhus IgM Microlisa kit. The manuscript was written adhering to Standards for Reporting Diagnostic Accuracy Studies (STARD) 2015 checklist[6].