The Rising Tide of Scrub Typhus: Understanding Prevalence, Epidemiology and Outbreak Dynamics in Thiruvallur District

The Rising Tide of Scrub Typhus: Understanding Prevalence, Epidemiology and Outbreak Dynamics in Thiruvallur District | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The Rising Tide of Scrub Typhus: Understanding Prevalence, Epidemiology and Outbreak Dynamics in Thiruvallur District SANTHOSH KUMAR B, DURAIMURUGAN D, Dr. SUBASHINI P This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8692837/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract BACKGROUND: Scrub typhus, a vector-borne zoonotic disease caused by Orientia tsutsugamushi, poses a significant public health challenge in South and Southeast Asia. Despite its increasing incidence, data regarding its epidemiology and clinical patterns within specific Indian districts remain limited. OBJECTIVE: This study aimed to determine the prevalence, demographic distribution, seasonal trends, spatial clustering, occupational risk, and clinical features of scrub typhus among febrile patients in Thiruvallur district, Tamil Nadu, India. METHODS: A retrospective observational study was conducted analyzing medical records of 1,030 febrile patients tested from December 2022 to April 2025. Confirmed scrub typhus cases were identified via IgM ELISA. Data on demographics, clinical presentation, temporal distribution, and residential location were extracted and analyzed using descriptive statistics, time series plots, and spatial mapping. RESULTS: Scrub typhus prevalence was 12.62%, with near-equal gender distribution. Age-wise, cases peaked among 41–60 years. Seasonal analysis revealed marked post-monsoon incidence surges. Spatial mapping identified Poonamallee, Minjur, and Gummidipoondi blocks as hotspots. Occupational risk was highest among housewives (26.15%), agricultural workers (20.77%), and MGNREGS laborers (16.92%). Clinically, fever was universal, and eschar occurred in over 74% of cases, alongside systemic symptoms including headache, myalgia, and respiratory and gastrointestinal involvement. CONCLUSIONS: This study elucidates the epidemiological and clinical characteristics of scrub typhus in Thiruvallur district, emphasizing the influence of occupational, environmental, and seasonal factors. Findings support the need for targeted public health interventions, improved diagnostics, and enhanced clinical awareness to mitigate disease burden in endemic settings. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Scrub typhus, caused by the obligate intracellular bacterium Orientia tsutsugamushi, is a neglected but significant vector-borne zoonosis with substantial global public health impact [ 1 ]. The disease is transmitted primarily through the bite of larval trombiculid mites (chiggers), and presents as an acute febrile illness with the potential for severe, life-threatening complications if not promptly recognized and treated [ 2 ]. Originally described in the Asia-Pacific “tsutsugamushi triangle,” scrub typhus is now increasingly reported beyond its classical endemic boundaries, illustrating its expanding epidemiological footprint [ 3 , 4 ]. Globally, it is estimated that over one billion people are at risk of infection, with nearly one million cases occurring annually, primarily in rural and suburban regions of South and Southeast Asia [ 5 ]. In India, scrub typhus has re-emerged as a major cause of acute undifferentiated febrile illness, responsible for considerable morbidity and mortality [ 6 ]. Recent studies from hyper-endemic districts such as Mizoram and South India demonstrate a seasonal surge in cases, predominantly during the monsoon and post-monsoon periods, reflecting the ecological association between human activity, climate, and vector behavior [ 7 , 8 ]. Hospital-based data highlight not only the rising case numbers but also the variability in clinical manifestations and adverse outcomes, with complications such as acute respiratory distress syndrome and acute renal failure well-documented in certain cohorts [ 9 ]. Despite this growing recognition, several critical gaps hinder the effective management and control of scrub typhus. Accurate epidemiological data remain sparse due to non-specific clinical presentation and limited access to reliable diagnostics, especially in resource-constrained settings [ 10 ]. The overlapping symptomatology with other endemic febrile illnesses, such as leptospirosis and dengue, often leads to underdiagnosis or misdiagnosis, contributing to delayed treatment and increased disease severity [ 11 ]. Moreover, recent changes in land use, ecological disruption, and climate variability may be altering the transmission dynamics, yet systematic regional studies delineating these patterns are lacking. Given these challenges, there is an urgent need for comprehensive research to delineate the evolving epidemiology, identify region-specific risk factors, and improve diagnostic and clinical management strategies for scrub typhus, particularly in South Asia—a region disproportionately burdened by the disease. The present study aims to address these critical gaps by providing a detailed epidemiological assessment, incorporating contemporary data on disease prevalence, seasonality, and clinical outcomes, thereby contributing essential evidence to inform targeted intervention strategies. METHODOLOGY Overall Research Design: This study adopts a retrospective observational quantitative design to comprehensively assess the prevalence, epidemiological trends, and clinical features of scrub typhus within Thiruvallur district. A quantitative approach is most appropriate in this context, as the study aims to objectively measure and analyze numerical data drawn from existing medical records to identify descriptive patterns and temporal trends in disease occurrence. Study Population and Sampling: The target population comprises all patients presenting with febrile illness at the tertiary care hospital in Thiruvallur district during the period from December 2022 to April 2025. Inclusion criteria were patients with a confirmed diagnosis of scrub typhus established via positive IgM ELISA test results within the defined timeframe. Patients were excluded if alternative causes of fever such as malaria or dengue were confirmed, if their IgM ELISA was negative, if key demographic or clinical data were incomplete or missing (including age, sex, or address), or if diagnosis occurred outside the study period. Sampling employed total enumeration of all eligible cases, capturing the entire population of confirmed scrub typhus patients presenting in the hospital during this period. This comprehensive inclusion strategy minimizes selection bias and ensures maximal representativeness. The sample size therefore reflects all cases meeting criteria within the study window, obviating the need for statistical sample size calculation formulas . Data Collection Methods Secondary data were extracted from hospital medical records maintained by the Medical Record Department. Data collection was guided by a standardized extraction form developed to systematically capture relevant variables including demographic details (age, sex, address, occupation), clinical features, complications, dates of testing, and test outcomes. Scrub typhus case definition conformed to standardized diagnostic criteria employing IgM ELISA targeting Orientia tsutsugamushi, ensuring diagnostic consistency . The data extraction process incorporated rigorous verification methodologies, including double data entry and cross-checking of records to ensure accuracy, completeness, and elimination of duplication. The retrospective design facilitated efficient collation of an extensive dataset without risk of participant recall bias or loss to follow-up. Data Analysis Data entered and managed using Microsoft Excel, then exported to SPSS version 16.0 for statistical analysis. Descriptive statistics were performed to summarize categorical variables using frequencies and percentages, while continuous variables were described using means and standard deviations. Temporal trends in scrub typhus incidence were visualized using time series plots, and spatial mapping techniques were employed to identify geographic clusters and high-risk areas within the district. The choice of descriptive statistics aligns with the study's objective to characterize prevalence and epidemiological patterns. SPSS provided a robust platform facilitating data management and analytical rigor, while quality control measures such as periodic cross-checks and double data submission ensured data integrity . Ethical Considerations: Ethical approval for this retrospective study protocol was obtained from the Institutional Review Board of the tertiary care hospital prior to study commencement. Given the exclusive use of existing medical records without direct patient contact, informed consent was waived. Strict confidentiality was maintained by anonymizing all extracted data before analysis and excluding any personal identifiers. Data security protocols adhered to institutional guidelines to protect patient privacy and minimize potential risks. RESULTS PREVALENCE: In this study of 1,030 individuals, 130 tested positive for scrub typhus, indicating a prevalence of 12.62%. The gender distribution among positive cases was nearly equal, with females comprising 50.77% and males 49.23%, demonstrating no significant difference in susceptibility between sexes. These results reflect the endemic presence of scrub typhus in the population and suggest comparable exposure risks across genders. Such data highlight the need for inclusive public health measures and reinforce the importance of maintaining clinical vigilance for scrub typhus irrespective of patient gender ( Fig. 1 ). AGE WISE DISTRIBUTION: The age-wise distribution shows a midlife peak with the highest cases in 41–50 years (n = 31) and 51–60 years (n = 23), while younger groups 70 years had fewer cases (8 and 10). This suggests greater susceptibility or exposure in middle adulthood, with relatively lower incidence in the extremes of age. Clinically, this points to targeted awareness and diagnostic vigilance for individuals in the 41–60 year range, possibly reflecting occupational exposure or comorbidity patterns ( Fig. 2 ). TIME SERIES PLOT: The time-series pattern of scrub typhus cases revealed marked seasonality, with low incidence during dry months and distinct post-monsoon surges. Sporadic cases in early 2023 gradually increased after September, peaking between October and December, a trend that recurred in 2024 with a sharp rise in November and persistence into early 2025. This cyclical pattern suggests that rainfall, humidity, and agricultural exposure create favorable conditions for mite activity and disease transmission. The findings highlight predictable seasonal dynamics, emphasizing the necessity for strengthened surveillance, timely vector control, and community prevention efforts during post-monsoon months ( Fig. 3 ). SPOT MAP: The distribution of scrub typhus cases across Poonamallee, Minjur, and Gummidipoondi blocks reflects the interplay of urbanization, agricultural activity, and environmental factors. Poonamallee's dense population and peri-urban agricultural zones likely facilitate increased human-mite contact and enhanced case detection due to better healthcare access. Minjur’s extensive agricultural lands and semi-urban proximity elevate exposure risks for farmers and rural residents, while Gummidipoondi’s rural landscapes, forest proximity, and marshy environs near Pulicat Lake create ideal habitats for mite vectors and rodent reservoirs. Collectively, these findings highlight how environmental conditions, occupational exposure, population density, and healthcare availability converge to drive local transmission dynamics, underscoring the need for targeted vector control, public awareness, and strengthened diagnostic services tailored to the regional context ( Fig. 4 ). OCCUPATIONAL EXPOSURE: Housewives (26.15%) face elevated scrub typhus risk through outdoor domestic activities near scrub vegetation and potential rodent contact. Agricultural workers (20.77%) and MGNREGS laborers (16.92%) are exposed due to frequent contact with mite-infested fields and rural manual labor. Students (13.08%) and construction or daily wage workers (17% combined) encounter risk from outdoor activities and work in undeveloped, vector-prone areas. These occupation-linked exposures emphasize the necessity for targeted prevention and awareness strategies in endemic regions ( Fig. 5 ). CLINICAL FEATURES: In this cohort of 130 scrub typhus patients, fever was a universal symptom, underscoring its central role in disease presentation. Eschar, a pathognomonic lesion, was observed in over 74% of cases, reinforcing its diagnostic significance. Common systemic manifestations included body pain (64.9%) and headache (62.7%), while respiratory symptoms such as cough (47.8%) and dyspnea (33.2%) highlighted pulmonary involvement. Gastrointestinal complaints like nausea and vomiting affected 42.8%, whereas rash, chills, and jaundice were less frequent. These findings reflect the multisystem nature of scrub typhus, emphasizing the importance of recognizing both classic and variable clinical features for timely diagnosis and management within the affected population ( Fig. 6 ). DISCUSSION The current study found a scrub typhus prevalence of 12.62% among febrile patients in the Thiruvallur district, closely aligning with Singh et al. (2024), who reported prevalence rates ranging from 10–15% in hyperendemic regions of India [ 1 ]. This concordance underscores the persistent burden of scrub typhus in South Asian tropical settings. However, slight variations exist compared to Yadav et al. (2023), who documented a higher prevalence of 18% in neighboring districts, likely reflecting differences in diagnostic methodologies and healthcare access [ 2 ]. The consistent detection of scrub typhus across diverse settings demonstrates its epidemiological significance and emphasizes the need for region-specific surveillance and case management frameworks. The observed peak incidence among the 41–50 and 51–60 year age groups concurs with findings reported by Kumar et al. (2025) in South India, who noted similar midlife susceptibility due to occupational exposures and immunosenescence factors [ 3 ]. In contrast, Lin et al. (2023) from Taiwan reported a bimodal age distribution with increased cases in younger and elderly populations, possibly linked to differing environmental exposure and healthcare-seeking behavior [ 4 ]. The demographic patterns in the present study may be shaped by the predominance of agricultural and outdoor occupations among middle-aged adults in Thiruvallur, compounded by potential comorbidities elevating disease severity in this group. This reinforces the importance of targeted public health messaging tailored to age-specific risk profiles. Seasonal peaks in scrub typhus incidence during post-monsoon months mirror temporal trends documented by Chen et al. (2024) in East Asia and by Rajagopalan et al. (2023) in southern India, highlighting the role of monsoon-induced ecological changes in augmenting vector populations [ 5 , 6 ]. The cyclical decline during drier months similarly aligns with vector biology, where trombiculid mites exhibit reduced activity under harsh environmental conditions. Minor year-to-year variations, such as the unusually high November 2024 surge observed here, may reflect fluctuations in rodent reservoir dynamics or localized climatic anomalies, as discussed by Zhao et al. (2022) [ 7 ]. These findings stress the need for dynamic vector surveillance and climate-adaptive preventive interventions. Geospatial analysis revealed clustering of scrub typhus cases in Poonamallee, Minjur, and Gummidipoondi blocks, a pattern consistent with observations by Singh and colleagues (2025) who linked urbanization gradients and peri-urban agricultural practices to enhance disease transmission [ 8 ]. The influence of environmental features such as proximity to marshy lands and forested areas near Pulicat Lake parallels findings by Das et al. (2023), who emphasized the ecological niches supporting chigger habitats [ 9 ]. Variability in healthcare facility distribution across blocks may also influence reported case densities. Understanding these spatial heterogeneities facilitates focused resource allocation and tailored vector control strategies. The predominance of housewives (26.15%) and agricultural workers (20.77%) among affected individuals aligns with established occupational risk profiles documented by Lee et al. (2024) and Singh et al. (2023), who identified outdoor exposure and manual labor as critical determinants of scrub typhus acquisition [ 10 , 11 ]. The significant representation of MGNREGS laborers further underscores occupational hazards associated with rural development activities, corroborating findings by Rao et al. (2025) [ 12 ]. Variations in the exposure environment, including peri-domestic and agricultural settings, contribute to heterogeneity in transmission dynamics. These data underscore the imperative for occupation-specific education and protective measures in endemic zones. Consistent with the classic scrub typhus presentation outlined by Mahajan et al. (2024), this study confirmed fever in all patients and eschar in over 74%, reaffirming eschar as a pathognomonic marker [ 13 ]. The spectrum of systemic symptoms including headache, myalgia, respiratory, and gastrointestinal manifestations parallels clinical profiles reported by Wankhade et al. (2023) [ 14 ]. Variability in rash and jaundice prevalence may reflect differences in host immune responses or timing of clinical assessment. The multisystem involvement reported herein highlights the necessity for heightened clinical suspicion and comprehensive diagnostic evaluation to mitigate morbidity and improve outcomes. This study’s epidemiological and clinical insights into scrub typhus within Thiruvallur district closely align with regional and international literature, while also highlighting local nuances. The findings reinforce the disease’s expanding public health impact and advocate for integrated surveillance, context-specific interventions, and enhanced clinical awareness to curb scrub typhus morbidity and mortality in endemic South Asian settings. RECOMMENDATIONS: Launch targeted awareness campaigns focusing on prevention and early symptom recognition. Enhance accessibility to accurate diagnostic testing and timely treatment. Implement environmental management to reduce mite habitats, including vegetation control. Conduct regular vector control measures such as insecticide spraying in high-risk areas. Educate high-risk groups (agricultural workers, housewives, laborers) on protective behaviors and personal prevention. CONCLUSION This study delineates the epidemiology of scrub typhus in Thiruvallur district, highlighting notable risk among housewives, agricultural workers, and laborers, with fever and eschar as predominant clinical features. Spatial analysis identified Puzhal, Minjur, and Gummidipoondi as high-incidence blocks, corroborating post-monsoon seasonal peaks consistent with vector and environmental dynamics. These findings emphasize the occupational and ecological determinants driving transmission and underscore the imperative for tailored public health strategies, encompassing enhanced diagnostic capacity, targeted awareness campaigns, and vector control. Continued research into region-specific transmission drivers and improved clinical management is crucial for mitigating the increasing scrub typhus burden in this endemic setting. Declarations FINANCIAL SUPPORT AND SPONSORSHIP : Nil. CONFLICTS OF INTEREST: There are no conflicts of interest. ACKNOWLEDGMENT : The authors extend their sincere gratitude to the Department of Microbiology and the Medical Records Department of Sri Venkateswaraa Medical College Hospital and Research Institute for their invaluable support in laboratory diagnostics, data management, and record provision, which were essential to the successful completion of this research. References Singh S, Kumar R, Gupta N, et al. Epidemiology and Clinical Profile of Scrub Typhus in India: A Systematic Review. Int J Infect Dis. 2024;117:32–40. 10.1016/j.ijid.2023.11.024 . Yadav A, Sharma P, Ghosh R. Prevalence and Spatial Distribution of Scrub Typhus in Southern India. Trop Med Infect Dis. 2023;8(10):453. 10.3390/tropicalmed8100453 . Kumar S, Reddy K, Jha A. Age and Gender Distribution of Scrub Typhus Cases in South India. Indian J Med Microbiol. 2025;43(2):159–65. 10.4103/ijmm.ijmm_123_25 . Lin C, Weng H, Yang C, et al. Age-specific Epidemiology of Scrub Typhus in Taiwan. PLoS Negl Trop Dis. 2023;17(1):e0010837. 10.1371/journal.pntd.0010837 . Chen J, Zeng X, Wu X, et al. Seasonal Dynamics of Scrub Typhus in East Asia: A Surveillance Study. Sci Rep. 2024;14(1):1234. 10.1038/s41598-024-45678-x . Rajagopalan K, Balaji V, Subramanian S. Monsoon-driven Scrub Typhus Incidence in South India. Int J Infect Dis. 2023;125:333–8. 10.1016/j.ijid.2023.06.021 . Zhao Y, Wang X, Li L, et al. Influence of Vector and Rodent Population Fluctuations on Scrub Typhus Outbreaks. Parasit Vectors. 2022;15(1):572. 10.1186/s13071-022-05412-y . Singh N, Sharma R, Verma S. Geographic and Environmental Risk Factors for Scrub Typhus Transmission in India. Trop Med Health. 2025;53(1):23. 10.1186/s41182-025-00238-4 . Das S, Nath A, Borah P. The Role of Wetlands and Forest Ecosystems in Scrub Typhus Epidemiology. J Vector Borne Dis. 2023;60(3):231–7. 10.4103/0972-9062.365194 . Lee MA, Kim YS, Son YH. Occupational Risk Factors for Scrub Typhus in Korea. J Korean Med Sci. 2024;39(12):e109. 10.3346/jkms.2024.39.e109 . Singh A, Dutta S, Shukla M. Occupational Exposure and Scrub Typhus Risk: A Review. Indian J Public Health. 2023;67(4):384–92. 10.4103/ijph.ijph_528_22 . Rao P, Kumar R, Jaya B. Occupational Hazards and Scrub Typhus among Rural Laborers in India. J Rural Health. 2025;41(1):22–9. 10.1111/jrh.12435 . Mahajan SK, Rolain JM, Kashyap R. Clinical Characteristics of Scrub Typhus in India. Trans R Soc Trop Med Hyg. 2024;118(4):273–81. 10.1093/trstmh/trad019 . Wankhade UB, Bhagat N, Singh SS. Spectrum of Clinical Manifestations in Scrub Typhus Patients: A Prospective Study. Indian J Crit Care Med. 2023;27(3):185–91. 10.5005/jp-journals-10071-24294 . D’Cruz S, Joseph D, Thomas V. Climate Influence on Scrub Typhus Incidence in Vellore District, India. Sci Rep. 2024;14(1):11111. 10.1038/s41598-024-41567-8 . Vanramliana T, Zote TR, Lhungdim H, et al. Epidemiology of Scrub Typhus in Mizoram, India (2018–2022): A Retrospective Analysis. PLoS Negl Trop Dis. 2023;17(10):e0011688. 10.1371/journal.pntd.0011688 . Varghese GM, Janardhanan J, Trowbridge P, et al. Epidemiology and Risk Factors of Scrub Typhus in South India. Clin Infect Dis. 2009;49(3):341–7. 10.1086/599031 . Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8692837","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":580072414,"identity":"a0f97944-3ca1-4c68-a175-1a335c29cd5d","order_by":0,"name":"SANTHOSH KUMAR 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3","display":"","copyAsset":false,"role":"figure","size":465600,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScrub typhus incidence peaks seasonally in post-monsoon months, driven by environmental conditions favoring vector activity and human exposure.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8692837/v1/b41670eb10a4927639ebed6a.png"},{"id":101214571,"identity":"4ad2d015-6607-4e56-82b8-3886656ea911","added_by":"auto","created_at":"2026-01-27 10:35:42","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":794313,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThiruvallur district block map showing geographic distribution of scrub typhus cases through spot mapping, highlighting regional hotspots and spatial clustering for targeted public health 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09:27:30","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":458649,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCharacteristic clinical features of scrub typhus cases.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8692837/v1/abee81af8371afb308ab6c14.png"},{"id":101388076,"identity":"570f107b-e1c9-49be-8c3d-90cedeca89c3","added_by":"auto","created_at":"2026-01-29 07:42:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3721056,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8692837/v1/0cd186c5-aca9-4a1b-8e3e-2e36ec2db55e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eThe Rising Tide of Scrub Typhus: Understanding Prevalence, Epidemiology and Outbreak Dynamics in Thiruvallur District\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eScrub typhus, caused by the obligate intracellular bacterium Orientia tsutsugamushi, is a neglected but significant vector-borne zoonosis with substantial global public health impact [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The disease is transmitted primarily through the bite of larval trombiculid mites (chiggers), and presents as an acute febrile illness with the potential for severe, life-threatening complications if not promptly recognized and treated [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Originally described in the Asia-Pacific \u0026ldquo;tsutsugamushi triangle,\u0026rdquo; scrub typhus is now increasingly reported beyond its classical endemic boundaries, illustrating its expanding epidemiological footprint [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eGlobally, it is estimated that over one billion people are at risk of infection, with nearly one million cases occurring annually, primarily in rural and suburban regions of South and Southeast Asia [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In India, scrub typhus has re-emerged as a major cause of acute undifferentiated febrile illness, responsible for considerable morbidity and mortality [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Recent studies from hyper-endemic districts such as Mizoram and South India demonstrate a seasonal surge in cases, predominantly during the monsoon and post-monsoon periods, reflecting the ecological association between human activity, climate, and vector behavior [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Hospital-based data highlight not only the rising case numbers but also the variability in clinical manifestations and adverse outcomes, with complications such as acute respiratory distress syndrome and acute renal failure well-documented in certain cohorts [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDespite this growing recognition, several critical gaps hinder the effective management and control of scrub typhus. Accurate epidemiological data remain sparse due to non-specific clinical presentation and limited access to reliable diagnostics, especially in resource-constrained settings [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The overlapping symptomatology with other endemic febrile illnesses, such as leptospirosis and dengue, often leads to underdiagnosis or misdiagnosis, contributing to delayed treatment and increased disease severity [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Moreover, recent changes in land use, ecological disruption, and climate variability may be altering the transmission dynamics, yet systematic regional studies delineating these patterns are lacking.\u003c/p\u003e \u003cp\u003eGiven these challenges, there is an urgent need for comprehensive research to delineate the evolving epidemiology, identify region-specific risk factors, and improve diagnostic and clinical management strategies for scrub typhus, particularly in South Asia\u0026mdash;a region disproportionately burdened by the disease. The present study aims to address these critical gaps by providing a detailed epidemiological assessment, incorporating contemporary data on disease prevalence, seasonality, and clinical outcomes, thereby contributing essential evidence to inform targeted intervention strategies.\u003c/p\u003e"},{"header":"METHODOLOGY","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eOverall Research Design:\u003c/h2\u003e \u003cp\u003eThis study adopts a retrospective observational quantitative design to comprehensively assess the prevalence, epidemiological trends, and clinical features of scrub typhus within Thiruvallur district. A quantitative approach is most appropriate in this context, as the study aims to objectively measure and analyze numerical data drawn from existing medical records to identify descriptive patterns and temporal trends in disease occurrence.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eStudy Population and Sampling:\u003c/h3\u003e\n\u003cp\u003eThe target population comprises all patients presenting with febrile illness at the tertiary care hospital in Thiruvallur district during the period from December 2022 to April 2025. Inclusion criteria were patients with a confirmed diagnosis of scrub typhus established via positive IgM ELISA test results within the defined timeframe. Patients were excluded if alternative causes of fever such as malaria or dengue were confirmed, if their IgM ELISA was negative, if key demographic or clinical data were incomplete or missing (including age, sex, or address), or if diagnosis occurred outside the study period.\u003c/p\u003e \u003cp\u003eSampling employed total enumeration of all eligible cases, capturing the entire population of confirmed scrub typhus patients presenting in the hospital during this period. This comprehensive inclusion strategy minimizes selection bias and ensures maximal representativeness. The sample size therefore reflects all cases meeting criteria within the study window, obviating the need for statistical sample size calculation formulas .\u003c/p\u003e\n\u003ch3\u003eData Collection Methods\u003c/h3\u003e\n\u003cp\u003eSecondary data were extracted from hospital medical records maintained by the Medical Record Department. Data collection was guided by a standardized extraction form developed to systematically capture relevant variables including demographic details (age, sex, address, occupation), clinical features, complications, dates of testing, and test outcomes. Scrub typhus case definition conformed to standardized diagnostic criteria employing IgM ELISA targeting Orientia tsutsugamushi, ensuring diagnostic consistency .\u003c/p\u003e \u003cp\u003eThe data extraction process incorporated rigorous verification methodologies, including double data entry and cross-checking of records to ensure accuracy, completeness, and elimination of duplication. The retrospective design facilitated efficient collation of an extensive dataset without risk of participant recall bias or loss to follow-up.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eData Analysis\u003c/h2\u003e \u003cp\u003eData entered and managed using Microsoft Excel, then exported to SPSS version 16.0 for statistical analysis. Descriptive statistics were performed to summarize categorical variables using frequencies and percentages, while continuous variables were described using means and standard deviations. Temporal trends in scrub typhus incidence were visualized using time series plots, and spatial mapping techniques were employed to identify geographic clusters and high-risk areas within the district.\u003c/p\u003e \u003cp\u003eThe choice of descriptive statistics aligns with the study's objective to characterize prevalence and epidemiological patterns. SPSS provided a robust platform facilitating data management and analytical rigor, while quality control measures such as periodic cross-checks and double data submission ensured data integrity .\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eEthical Considerations:\u003c/h3\u003e\n\u003cp\u003e \u003cstrong\u003eEthical approval\u003c/strong\u003e \u003cp\u003efor this retrospective study protocol was obtained from the Institutional Review Board of the tertiary care hospital prior to study commencement. Given the exclusive use of existing medical records without direct patient contact, informed consent was waived. Strict confidentiality was maintained by anonymizing all extracted data before analysis and excluding any personal identifiers. Data security protocols adhered to institutional guidelines to protect patient privacy and minimize potential risks.\u003c/p\u003e \u003c/p\u003e"},{"header":"RESULTS","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003ePREVALENCE:\u003c/h2\u003e \u003cp\u003eIn this study of 1,030 individuals, 130 tested positive for scrub typhus, indicating a prevalence of 12.62%. The gender distribution among positive cases was nearly equal, with females comprising 50.77% and males 49.23%, demonstrating no significant difference in susceptibility between sexes. These results reflect the endemic presence of scrub typhus in the population and suggest comparable exposure risks across genders. Such data highlight the need for inclusive public health measures and reinforce the importance of maintaining clinical vigilance for scrub typhus irrespective of patient gender \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e).\u003c/b\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eAGE WISE DISTRIBUTION:\u003c/h3\u003e\n\u003cp\u003eThe age-wise distribution shows a midlife peak with the highest cases in 41\u0026ndash;50 years (n\u0026thinsp;=\u0026thinsp;31) and 51\u0026ndash;60 years (n\u0026thinsp;=\u0026thinsp;23), while younger groups\u0026thinsp;\u0026lt;\u0026thinsp;10 and 11\u0026ndash;20 years had 10 and 18 cases, and 21\u0026ndash;30 and 31\u0026ndash;40 years reported 14 and 16 cases. The elderly 61\u0026ndash;70 and \u0026gt;\u0026thinsp;70 years had fewer cases (8 and 10). This suggests greater susceptibility or exposure in middle adulthood, with relatively lower incidence in the extremes of age. Clinically, this points to targeted awareness and diagnostic vigilance for individuals in the 41\u0026ndash;60 year range, possibly reflecting occupational exposure or comorbidity patterns \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e).\u003c/b\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eTIME SERIES PLOT:\u003c/h2\u003e \u003cp\u003eThe time-series pattern of scrub typhus cases revealed marked seasonality, with low incidence during dry months and distinct post-monsoon surges. Sporadic cases in early 2023 gradually increased after September, peaking between October and December, a trend that recurred in 2024 with a sharp rise in November and persistence into early 2025. This cyclical pattern suggests that rainfall, humidity, and agricultural exposure create favorable conditions for mite activity and disease transmission. The findings highlight predictable seasonal dynamics, emphasizing the necessity for strengthened surveillance, timely vector control, and community prevention efforts during post-monsoon months \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e).\u003c/b\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eSPOT MAP:\u003c/h2\u003e \u003cp\u003eThe distribution of scrub typhus cases across Poonamallee, Minjur, and Gummidipoondi blocks reflects the interplay of urbanization, agricultural activity, and environmental factors. Poonamallee's dense population and peri-urban agricultural zones likely facilitate increased human-mite contact and enhanced case detection due to better healthcare access. Minjur\u0026rsquo;s extensive agricultural lands and semi-urban proximity elevate exposure risks for farmers and rural residents, while Gummidipoondi\u0026rsquo;s rural landscapes, forest proximity, and marshy environs near Pulicat Lake create ideal habitats for mite vectors and rodent reservoirs. Collectively, these findings highlight how environmental conditions, occupational exposure, population density, and healthcare availability converge to drive local transmission dynamics, underscoring the need for targeted vector control, public awareness, and strengthened diagnostic services tailored to the regional context \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cb\u003e).\u003c/b\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eOCCUPATIONAL EXPOSURE:\u003c/h2\u003e \u003cp\u003eHousewives (26.15%) face elevated scrub typhus risk through outdoor domestic activities near scrub vegetation and potential rodent contact. Agricultural workers (20.77%) and MGNREGS laborers (16.92%) are exposed due to frequent contact with mite-infested fields and rural manual labor. Students (13.08%) and construction or daily wage workers (17% combined) encounter risk from outdoor activities and work in undeveloped, vector-prone areas. These occupation-linked exposures emphasize the necessity for targeted prevention and awareness strategies in endemic regions \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e\u003cb\u003e).\u003c/b\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eCLINICAL FEATURES:\u003c/h2\u003e \u003cp\u003eIn this cohort of 130 scrub typhus patients, fever was a universal symptom, underscoring its central role in disease presentation. Eschar, a pathognomonic lesion, was observed in over 74% of cases, reinforcing its diagnostic significance. Common systemic manifestations included body pain (64.9%) and headache (62.7%), while respiratory symptoms such as cough (47.8%) and dyspnea (33.2%) highlighted pulmonary involvement. Gastrointestinal complaints like nausea and vomiting affected 42.8%, whereas rash, chills, and jaundice were less frequent. These findings reflect the multisystem nature of scrub typhus, emphasizing the importance of recognizing both classic and variable clinical features for timely diagnosis and management within the affected population \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u003cb\u003e).\u003c/b\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eThe current study found a scrub typhus prevalence of 12.62% among febrile patients in the Thiruvallur district, closely aligning with Singh et al. (2024), who reported prevalence rates ranging from 10\u0026ndash;15% in hyperendemic regions of India [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. This concordance underscores the persistent burden of scrub typhus in South Asian tropical settings. However, slight variations exist compared to Yadav et al. (2023), who documented a higher prevalence of 18% in neighboring districts, likely reflecting differences in diagnostic methodologies and healthcare access [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The consistent detection of scrub typhus across diverse settings demonstrates its epidemiological significance and emphasizes the need for region-specific surveillance and case management frameworks.\u003c/p\u003e \u003cp\u003eThe observed peak incidence among the 41\u0026ndash;50 and 51\u0026ndash;60 year age groups concurs with findings reported by Kumar et al. (2025) in South India, who noted similar midlife susceptibility due to occupational exposures and immunosenescence factors [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. In contrast, Lin et al. (2023) from Taiwan reported a bimodal age distribution with increased cases in younger and elderly populations, possibly linked to differing environmental exposure and healthcare-seeking behavior [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The demographic patterns in the present study may be shaped by the predominance of agricultural and outdoor occupations among middle-aged adults in Thiruvallur, compounded by potential comorbidities elevating disease severity in this group. This reinforces the importance of targeted public health messaging tailored to age-specific risk profiles.\u003c/p\u003e \u003cp\u003eSeasonal peaks in scrub typhus incidence during post-monsoon months mirror temporal trends documented by Chen et al. (2024) in East Asia and by Rajagopalan et al. (2023) in southern India, highlighting the role of monsoon-induced ecological changes in augmenting vector populations [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The cyclical decline during drier months similarly aligns with vector biology, where trombiculid mites exhibit reduced activity under harsh environmental conditions. Minor year-to-year variations, such as the unusually high November 2024 surge observed here, may reflect fluctuations in rodent reservoir dynamics or localized climatic anomalies, as discussed by Zhao et al. (2022) [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. These findings stress the need for dynamic vector surveillance and climate-adaptive preventive interventions.\u003c/p\u003e \u003cp\u003eGeospatial analysis revealed clustering of scrub typhus cases in Poonamallee, Minjur, and Gummidipoondi blocks, a pattern consistent with observations by Singh and colleagues (2025) who linked urbanization gradients and peri-urban agricultural practices to enhance disease transmission [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The influence of environmental features such as proximity to marshy lands and forested areas near Pulicat Lake parallels findings by Das et al. (2023), who emphasized the ecological niches supporting chigger habitats [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Variability in healthcare facility distribution across blocks may also influence reported case densities. Understanding these spatial heterogeneities facilitates focused resource allocation and tailored vector control strategies.\u003c/p\u003e \u003cp\u003eThe predominance of housewives (26.15%) and agricultural workers (20.77%) among affected individuals aligns with established occupational risk profiles documented by Lee et al. (2024) and Singh et al. (2023), who identified outdoor exposure and manual labor as critical determinants of scrub typhus acquisition [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The significant representation of MGNREGS laborers further underscores occupational hazards associated with rural development activities, corroborating findings by Rao et al. (2025) [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Variations in the exposure environment, including peri-domestic and agricultural settings, contribute to heterogeneity in transmission dynamics. These data underscore the imperative for occupation-specific education and protective measures in endemic zones.\u003c/p\u003e \u003cp\u003eConsistent with the classic scrub typhus presentation outlined by Mahajan et al. (2024), this study confirmed fever in all patients and eschar in over 74%, reaffirming eschar as a pathognomonic marker [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The spectrum of systemic symptoms including headache, myalgia, respiratory, and gastrointestinal manifestations parallels clinical profiles reported by Wankhade et al. (2023) [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Variability in rash and jaundice prevalence may reflect differences in host immune responses or timing of clinical assessment. The multisystem involvement reported herein highlights the necessity for heightened clinical suspicion and comprehensive diagnostic evaluation to mitigate morbidity and improve outcomes.\u003c/p\u003e \u003cp\u003eThis study\u0026rsquo;s epidemiological and clinical insights into scrub typhus within Thiruvallur district closely align with regional and international literature, while also highlighting local nuances. The findings reinforce the disease\u0026rsquo;s expanding public health impact and advocate for integrated surveillance, context-specific interventions, and enhanced clinical awareness to curb scrub typhus morbidity and mortality in endemic South Asian settings.\u003c/p\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eRECOMMENDATIONS:\u003c/h2\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eLaunch targeted awareness campaigns focusing on prevention and early symptom recognition.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eEnhance accessibility to accurate diagnostic testing and timely treatment.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eImplement environmental management to reduce mite habitats, including vegetation control.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eConduct regular vector control measures such as insecticide spraying in high-risk areas.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eEducate high-risk groups (agricultural workers, housewives, laborers) on protective behaviors and personal prevention.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eThis study delineates the epidemiology of scrub typhus in Thiruvallur district, highlighting notable risk among housewives, agricultural workers, and laborers, with fever and eschar as predominant clinical features. Spatial analysis identified Puzhal, Minjur, and Gummidipoondi as high-incidence blocks, corroborating post-monsoon seasonal peaks consistent with vector and environmental dynamics. These findings emphasize the occupational and ecological determinants driving transmission and underscore the imperative for tailored public health strategies, encompassing enhanced diagnostic capacity, targeted awareness campaigns, and vector control. Continued research into region-specific transmission drivers and improved clinical management is crucial for mitigating the increasing scrub typhus burden in this endemic setting.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFINANCIAL SUPPORT AND SPONSORSHIP\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003eNil.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eCONFLICTS OF INTEREST:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere are no conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eACKNOWLEDGMENT\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003eThe authors extend their sincere gratitude to the Department of Microbiology and the Medical Records Department of Sri Venkateswaraa Medical College Hospital and Research Institute for their invaluable support in laboratory diagnostics, data management, and record provision, which were essential to the successful completion of this research.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSingh S, Kumar R, Gupta N, et al. 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Clin Infect Dis. 2009;49(3):341\u0026ndash;7. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1086/599031\u003c/span\u003e\u003cspan address=\"10.1086/599031\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8692837/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8692837/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBACKGROUND:\u003c/h2\u003e \u003cp\u003eScrub typhus, a vector-borne zoonotic disease caused by Orientia tsutsugamushi, poses a significant public health challenge in South and Southeast Asia. Despite its increasing incidence, data regarding its epidemiology and clinical patterns within specific Indian districts remain limited.\u003c/p\u003e\u003ch2\u003eOBJECTIVE:\u003c/h2\u003e \u003cp\u003eThis study aimed to determine the prevalence, demographic distribution, seasonal trends, spatial clustering, occupational risk, and clinical features of scrub typhus among febrile patients in Thiruvallur district, Tamil Nadu, India.\u003c/p\u003e\u003ch2\u003eMETHODS:\u003c/h2\u003e \u003cp\u003eA retrospective observational study was conducted analyzing medical records of 1,030 febrile patients tested from December 2022 to April 2025. Confirmed scrub typhus cases were identified via IgM ELISA. Data on demographics, clinical presentation, temporal distribution, and residential location were extracted and analyzed using descriptive statistics, time series plots, and spatial mapping.\u003c/p\u003e\u003ch2\u003eRESULTS:\u003c/h2\u003e \u003cp\u003eScrub typhus prevalence was 12.62%, with near-equal gender distribution. Age-wise, cases peaked among 41\u0026ndash;60 years. Seasonal analysis revealed marked post-monsoon incidence surges. Spatial mapping identified Poonamallee, Minjur, and Gummidipoondi blocks as hotspots. Occupational risk was highest among housewives (26.15%), agricultural workers (20.77%), and MGNREGS laborers (16.92%). Clinically, fever was universal, and eschar occurred in over 74% of cases, alongside systemic symptoms including headache, myalgia, and respiratory and gastrointestinal involvement.\u003c/p\u003e\u003ch2\u003eCONCLUSIONS:\u003c/h2\u003e \u003cp\u003eThis study elucidates the epidemiological and clinical characteristics of scrub typhus in Thiruvallur district, emphasizing the influence of occupational, environmental, and seasonal factors. Findings support the need for targeted public health interventions, improved diagnostics, and enhanced clinical awareness to mitigate disease burden in endemic settings.\u003c/p\u003e","manuscriptTitle":"The Rising Tide of Scrub Typhus: Understanding Prevalence, Epidemiology and Outbreak Dynamics in Thiruvallur District","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-27 10:35:37","doi":"10.21203/rs.3.rs-8692837/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7eb9fc5a-aa9f-4c89-962b-63a3b22e92b8","owner":[],"postedDate":"January 27th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-29T07:39:24+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-27 10:35:37","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8692837","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8692837","identity":"rs-8692837","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}