Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi, an obligate intracellular bacterium transmitted by the larval stage of trombiculid mites, commonly known as chiggers [1,2]. It is a major but often neglected public health problem in Asia, including India, where the disease has shown a resurgence in recent years. Globally, nearly one billion people are estimated to be at risk, and approximately one million cases occur annually [3]. The term “scrub” refers to the typical habitat of the vector—areas with dense vegetation—although the infection is now reported from varied ecological settings such as plains, agricultural fields, and coastal regions [4]. Historically, scrub typhus was first recognized in India during World War II among soldiers stationed in Assam and West Bengal [5]. Over time, its distribution expanded beyond the sub-Himalayan belt, with outbreaks documented in states such as Haryana, Punjab, Rajasthan, and southern regions like Kerala and Tamil Nadu [6–9]. This changing epidemiology challenges the earlier belief that scrub typhus is confined to hilly terrain and highlights its presence in semi-arid and urban areas [10]. Clinically, scrub typhus presents with nonspecific symptoms such as fever, headache, myalgia, and lymphadenopathy, making it difficult to distinguish from other causes of acute febrile illness like malaria, dengue, and typhoid [11,12]. Severe cases may progress to complications including hepatitis, acute respiratory distress syndrome (ARDS), renal failure, and multi-organ dysfunction syndrome (MODS) [10]. A characteristic eschar at the site of the mite bite is considered diagnostic, but its detection is often missed in Indian patients due to darker skin tones and variable occurrence [13,14]. If untreated, mortality can range from 7% to 30%, underscoring the importance of early diagnosis and treatment [15]. Despite its growing prevalence, scrub typhus remains underdiagnosed in regions like Haryana, where clinicians rarely consider it in differential diagnoses of febrile illness [10]. Understanding its epidemiology and clinical correlations in such areas is essential for timely recognition and management. This pilot study was conducted to determine the proportion of scrub typhus among patients presenting with acute febrile illness in a tertiary care hospital in Haryana and to assess associated coinfections and laboratory parameters

Study Design and Setting A hospital-based cross-sectional observational study was conducted over a period of six months (July 2022 to November 2022) at the Departments of Microbiology and General Medicine, SGT Medical College, Hospital and Research Institute, Gurugram, Haryana, India. Study Participants A total of 86 consecutive patients presenting with acute febrile illness (AFI) were enrolled in the study. Patients of either gender and all age groups attending the Medicine outpatient department or admitted during the study period were included after obtaining informed consent. Inclusion Criteria Patients presenting with fever of ≤14 days duration with clinical suspicion of acute febrile illness were included. Sample Collection From each enrolled patient, 5 mL of venous blood was collected under aseptic precautions. Serum was separated by centrifugation at 3500 rpm for 15 minutes and stored at 2–8°C until testing. Serological Testing for Scrub Typhus Detection of IgM antibodies against Orientia tsutsugamushi was performed using a commercial Scrub Typhus Detect™ IgM ELISA kit (InBios International Inc., USA) in accordance with the manufacturer’s instructions (Figure-1). Briefly, diluted serum samples were added to antigen-coated microtitre wells and incubated. After washing, enzyme-conjugated anti-human IgM was added, followed by substrate solution. The reaction was stopped and absorbance was read at 450 nm using an ELISA reader. Results were interpreted as positive or negative based on the cut-off values provided by the manufacturer. Positive and negative controls were included in each run (Figure-2). Detection of Co-Infections Patients positive for scrub typhus were further evaluated for co-infections, including dengue fever, malaria, and enteric fever, using standard laboratory diagnostic methods available at the institution. Laboratory Parameters Hematological and biochemical parameters such as platelet count, serum glutamic oxaloacetic transaminase (SGOT), and serum glutamic pyruvic transaminase (SGPT) were recorded and analyzed. Statistical Analysis Data were entered into Microsoft Excel and analyzed statistically. Continuous variables were expressed as mean ± standard deviation, while categorical variables were expressed as frequency and percentage. Correlation between scrub typhus seropositivity and laboratory parameters was assessed using Pearson’s correlation coefficient. A p-value <0.05 was considered statistically significant. Ethical Approval The study was approved by the Institutional Ethics Committee of SGT University, and written informed consent was obtained from all participants prior to enrollment.

In the present hospital-based cross-sectional study, scrub typhus IgM antibodies were detected in 26 out of 86 patients (30.23%) presenting with acute febrile illness. (Graph-1) This finding highlights scrub typhus as a significant and under recognized cause of acute undifferentiated fever in tertiary care settings. Similar prevalence rates have been reported from different parts of North India, where scrub typhus accounted for 14–30% of acute febrile illness cases, emphasizing its re-emergence beyond traditionally endemic regions [16-18]. A male predominance (69.23%) was observed among scrub typhus positive cases, with a male-to-female ratio of approximately 2.2:1. (Table 1, Graph 2) This observation is consistent with previous studies reporting higher incidence among males, likely due to increased outdoor and occupational exposure to mite-infested environments such as agricultural fields and scrub vegetation [19,20]. The most commonly affected age group in this study was 20–30 years, indicating that young adults are at greater risk, which contrasts with some reports showing higher prevalence in older age groups but aligns with studies conducted in active working populations (Table 2, Graph 3) [21]. Co-infections were identified in a substantial proportion of scrub typhus positive patients. Dengue fever was the most frequent co-infection (34.61%), followed by enteric fever (15.38%) and malaria (3.85%). (Table 3, Graph 4) The occurrence of scrub typhus–dengue co-infection has been widely reported in India due to overlapping seasonal patterns, similar vector ecology, and comparable clinical presentations [22,23]. These co-infections complicate clinical diagnosis and may delay appropriate treatment, increasing the risk of complications. Thrombocytopenia was a prominent laboratory abnormality among scrub typhus patients. A statistically significant negative correlation was observed between scrub typhus seropositivity and platelet count (r = −0.407, p < 0.05), indicating that declining platelet levels are associated with disease severity (Table 4, Graph 5). Thrombocytopenia in scrub typhus is believed to result from endothelial damage, immune-mediated platelet destruction, and consumption due to microangiopathic processes, similar to mechanisms described in dengue and other rickettsial infections [24,25]. Hepatic involvement was also evident in the present study, as reflected by elevated SGOT and SGPT levels, although the correlation with scrub typhus seropositivity was not statistically significant (Table 5, Graph 6 & Graph 7). Mild to moderate transaminase elevation is a well-documented finding in scrub typhus and is attributed to hepatic inflammation secondary to systemic vasculitis and cytokine-mediated injury [26,27]. Comparable elevations in liver enzymes have been reported in studies from Nepal, South India, and North India, supporting hepatic dysfunction as a common manifestation of scrub typhus infection [28,29]. Interestingly, no eschar was detected in any of the scrub typhus positive patients in this study. This finding is consistent with several Indian studies reporting a low prevalence of eschar, possibly due to darker skin pigmentation, concealed bite sites, or lack of meticulous clinical examination [30]. The absence of eschar further underscores the diagnostic challenge posed by scrub typhus and reinforces the need for laboratory confirmation in suspected cases. Seasonal analysis revealed a higher number of scrub typhus cases during the monsoon and post-monsoon months, which correlates with increased mite activity and enhanced human exposure to vector habitats. Similar seasonal trends have been documented across India and other endemic regions, supporting the role of climatic and ecological factors in disease transmission [31,32]. Overall, the findings of this study demonstrate that scrub typhus is not confined to classical endemic regions and should be considered a critical differential diagnosis in acute febrile illness, especially when associated with thrombocytopenia and hepatic dysfunction. Early serological testing and prompt initiation of appropriate antibiotic therapy are essential to reduce morbidity and prevent severe complications [33]. Sex-wise distribution Table 1 - Distribution of study participants according to gender Gender No. of Patients Percentage Female 8 30.77% Male 18 69.23% Distribution of study participants according to age Table 2 - Distribution of study participants according to age Age groups No. of patients Percentage 10-20 Years 3 11.54% 20-30 Years 11 42.31% 30-40 Years 5 19.23% 40-50 Years 4 15.38% ≥50 Years 3 11.54% Distribution of Co-infections Table 3 - Distribution of study participants according to co-infection Co-Infection No. of Patients Percentage Dengue 9 34.61% Widal 4 15.38% Malaria 1 3.85% correlation of scrub typhus among platelet count Table 4 - Correlation of scrub typhus among platelet count Platelet in lac Scrub typhus Pearson Correlation -0.407 p-value 0.039* Correlation of Scrub typhus among SGOT & SGPT Table 5 - Correlation of Scrub typhus among SGOT & SGP SGOT SGPT Scrub typhus Pearson Correlation 0.260 -0.121 p-value 0.199 0.555

1. Bonell A, Lubell Y, Newton PN, Crump JA, Paris DH. Estimating the burden of scrub typhus: A systematic review. PLoS Negl Trop Dis. 2017;11:e0005838. 2. Behera B, Biswal M, Das RR, et al. Clinico-epidemiological analysis of scrub typhus in hospitalised patients presenting with acute undifferentiated febrile illness: A hospital-based study from Eastern India. Indian J Med Microbiol. 2019;37:278-80. 3. Aggarwal HK, Jain D, Kaverappa V, Mittal A, Yadav S, Gupta A. Emergence of scrub typhus in northern India: Experience from tertiary care hospital. KLIMIK Derg 2015;27:6–11. 4. Paris DH, Shelite TR, Day NP, Walker DH. Unresolved problems related to scrub typhus: a seriously neglected life-threatening disease. Am J Trop Med Hyg. 2013;89:301–7. 5. Sharma N, Biswal M, Kumar A, Zaman K, Jain S, Bhalla A. Scrub typhus in a tertiary care hospital in north India. Am J Trop Med Hyg 2016;95:447–51. 6. Masand R, Yadav R, Purohit A, Tomar BS. Scrub typhus in rural Rajasthan and a review of other Indian studies Paediatr int child health. 2016;36:148-53.. 7. Sivarajan S, Shivalli S, Bhuyan D, Mawlong M, Barman R. Clinical and paraclinical profile, and predictors of outcome in 90 cases of scrub typhus, Meghalaya, India. Infect. Dis. Poverty 2016;5:47-56. 8. Walker DH, Dumler S, Marrie T. 211: Rickettsial Diseases. In: Longo DL, Kasper DL, Jameson JL, Fauci AS, Hauser SL, Loscalzo J, et al., (eds.). Harrison’s principles of internal medicine. 19th ed. New York :McGraw Hill; 2015, pp: 1154-62. 9. Bhargava A, Kaushik R, Kaushik R, Sharma A, Ahmad S, Dhar M, et al. Scrub typhus in Uttarakhand & adjoining Uttar Pradesh: Seasonality, clinical presentations & predictors of mortality. Indian J Med Res. 2016;144:901-9. 10. Jain D, Nand N, Giri K, Bhutani J. Scrub typhus infection, not a benign disease: an experience from a tertiary care center in Northern India. Med Pharm Rep. 2019;92:36–42. 11. Rao PN, Van Eijk AM, Choubey S et al. Dengue, chikungunya, and scrub typhus are important etiologies of non-malarial febrile illness in Rourkela, Odisha, India. BMC Infect. Dis. 2019;19:1-3. 12. Robinson ML, Kadam D, Khadse S, et al. Vector-borne disease is a common cause of hospitalized febrile illness in India. Am J Trop Med Hyg. 2018;98:1526-33. 13. Rose W, Rajan RJ, Punnen A, Ghosh U: Distribution of eschar in pediatric scrub typhus . J Trop Pediatr. 2016, 62:415-20. 10.1093/tropej/fmw027 14. Arun Babu T, Vijayadevagaran V, Ananthakrishnan S: Characteristics of pediatric scrub typhus eschar in South Indian children. Pediatr Dermatol. 2017, 34:124-7. 10. 15. Takhar RP, Bunkar ML, Arya S, Mirdha N. A scrub typhus: A prospective, observational study during an outbreak in Rajasthan, India. Natl Med J India 2017;30:69 72. 16. Devasagayam E, Dayanand D, Kundu D, Kamath MS, Kirubakaran R, Varghese GM. The burden of scrub typhus in India: A systematic review. PLoS Negl Trop Dis. 2021;15(7):e0009619. 17. Yadav J, Chenchula S, Nema RK, Choudhari JK, Purwar S. Sero-diagnosis of scrub typhus infection in India: A systematic review and meta-analysis. Trop Med Int Health. 2026. doi:10.1111/tmi.70185. 18. Chaturvedi R, Hussain SSA, Sampath H, Rahi M, Mirdha BR, Sharma A. Spatiotemporal epidemiology and clinical manifestations of two decades of scrub typhus in India: A systematic review and meta-analysis. BMJ Glob Health. 2025;10(8):e018998. 19. Vivekanandan M, Mani A, Priya YS, Singh AP, Jayakumar S, Purty S. Outbreak of scrub typhus in Pondicherry. J Assoc Physicians India. 2010;58:24-28. 20. Varghese GM, Abraham OC, Mathai D, et al. Scrub typhus among hospitalised patients with febrile illness in South India: Magnitude and clinical predictors. J Infect. 2006;52(1):56-60. 21. Bhargava A, Kaushik R, Kaushik RM, et al. Scrub typhus in Uttarakhand and adjoining Uttar Pradesh: Seasonality, clinical presentations and predictors of mortality. Trop Doct. 2016;46(1):39-42. 22. Chandra A, Hati A, Ray AK, Chakraborty U, Karmakar PS, Dasgupta S. Dengue and scrub typhus coinfection: A diagnostic dilemma. Oman Med J. 2023;38(3):e513. 23. Pokhrel A, et al. Coinfection of scrub typhus with dengue, malaria and typhoid fever in acute febrile illness: A hospital-based study. J Nepal Health Res Counc. 2021;19(2):322-327. 24. Patel M, Acharya S, Shukla S, Nimkar S, Kumar S. Scrub typhus induced thrombotic thrombocytopenia: A rare case report. J Clin Diagn Res. 2025. 25. Kim DM, Won KJ, Park CY, Yu KD, Kim HS, Yang TY. Distribution of eschars on the body of scrub typhus patients: A prospective study. Am J Trop Med Hyg. 2007;76(4):806-809. 26. Sharma M, Gupta S, Tripathi D, et al. Clinical and biochemical profile of scrub typhus patients with emphasis on liver dysfunction in a tertiary care centre in South Rajasthan. Int J Res Med Sci. 2024;12(8):2814-2820. 27. Dwivedi S, Gaikwad K, Ansari YM, et al. Hepatic dysfunction among scrub typhus Indian patients with acute undifferentiated febrile illness. Bioinformation. 2025;21(2):137-144. 28. Shrestha S, et al. Clinical and biochemical profile of scrub typhus patients in Nepal. BMC Res Notes. 2018;11:713. 29. Tyagi S, Rahaengdale N, Shukla N, Kiran VR. Analysis of clinical and biochemical parameters in scrub typhus patients in Central India. Int J Pharm Clin Res. 2023;15(10):616-620. 30. Koraluru M, Bairy I, Varma M, et al. Diagnostic challenge of scrub typhus in India: Evaluation of eschar prevalence and clinical profile. J Infect Public Health. 2015;8(4):328-333. 31. Khan SA, Dutta P, Topno R, et al. Seasonal activity of scrub typhus in North-East India. J Vector Borne Dis. 2015;52(2):152-155. 32. Mehta A, Goel A, Singh C. The re-emerging shadow: A systematic review of scrub typhus in India. J Assoc Med Sci. 2026. 33. Mehta A, Maravi DS, Ajmariya M. Re-emergence of scrub typhus in India: A systematic review and meta-analysis of prevalence and fatality. J Vector Borne Dis. 2026.