Pneumonia Due to Scrub Typhus Infection of Unknown Origin: A Case Report

Background: Scrub typhus is an acute febrile illness caused by the rickettsial bacterium Orientia tsutsugamushi , transmitted to humans through infected mite bites. Patients typically present with sudden high fever, headache, myalgia, and eschar formation at the site of the bites. Respiratory symptoms, such as cough and shortness of breath, can also occur, especially in severe cases that lead to pneumonia, organ failure, or acute respiratory distress syndrome (ARDS). This report presents a case of scrub typhus pneumonia of unknown origin, diagnosed by metagenomic next-generation sequencing (mNGS) of bronchoalveolar lavage fluid. Case Presentation: A 58-year-old woman was admitted with cough, sputum production, and fever. Imaging revealed pneumonia. During hospitalization, bronchoscopy was performed to identify the causative pathogen. mNGS of the bronchoalveolar lavage fluid confirmed Orientia tsutsugamushi infection. the patient's pneumonia was improved after oral administration of doxycycline(100mg, tid) for anti-infection treatment for 1 month. Conclusion: This report highlights the diagnostic challenges of scrub typhus-induced pneumonia and demonstrates the advantages of mNGS in identifying rare pathogens. It also underscores the importance of standardized antibiotic therapy for treating scrub typhus pneumonia.