Emerging Rickettsial Diseases among Patients Presenting with Acute Undifferentiated Febrile Illness: A Crosssectional Observational Study from a Tertiary Care Hospital of Manipur, India

Introduction: There has been an increase in the occurrence of Rickettsial Diseases (RDs) across the country, causing a widespread health burden. Although very few studies have been conducted on Scrub Typhus (ST) in Manipur, limited information on other RDs is available. Aim: To determine the prevalence of emerging RDs among patients with Acute Undifferentiated Febrile Illness (AUFI) in Manipur, India. Materials and Methods: A cross-sectional observational study was conducted at the Viral Research and Diagnostic Laboratory (VRDL), Department of Microbiology, Jawaharlal Nehru Institute of Medical Sciences, Imphal, Manipur, India from January 2021 to December 2025. The study included 4,959 patients of all age groups and both sexes presenting with AUFI and attending either the Outpatient (OPD) or Inpatient Departments (IPD). Serum samples were tested for ST, Spotted Fever Group (SFG), and Typhus Group (TG) infections using IgM Enzyme Linked Immunosorbent Assay (ELISA). Seropositive samples and eschar tissues were further analysed by real-time Polymerase Chain Reaction (PCR) for the detection of Orientia tsutsugamushi-specific DNA. Results: Among the 4,959 participants enrolled, ELISA detected ST in 604 (12.18%), SFG rickettsiae in 207 (4.17%), and TG rickettsioses in 102 (2.06%). PCR confirmed ST in 64 (22.22%) seropositive cases. Disease incidence peaked during the monsoon and post-monsoon seasons, and it was higher in rural populations, 594 (65.06%), than in urban populations, 319 (34.94%). The most common clinical features among ST cases were headache 433 (71.69%), followed by cough 402 (66.56%), anorexia 375 (62.09%), myalgia 325 (53.81%), and arthralgia 309 (51.16%). Nausea/vomiting was observed in 296 (49.01%) cases, while rash was observed in 151 (25.00%) and eschar in 103 (17.05%) cases. The major complications were encephalopathy 49 (8.11%), acute renal injury 45 (7.45%), and bleeding manifestations 39 (6.46%). Conclusion: The study established that three emerging RDs were circulating in Manipur, particularly during the monsoon and post-monsoon periods. Furthermore, it underscored that rickettsial infections are a major cause of AUFI, indicating they should be considered in the differential diagnosis to ensure early diagnosis and appropriate treatment.