Abstract: Objective To explore the clinical characteristics, diagnostic difficulties, and treatment strategies of a case of Q fever with fever of unknown origin as the main manifestation, which was complicated by an infection following the implantation of a thoracoabdominal aortic aneurysm stent. Methods Anti-infective treatments involving ceftriaxone, ornidazole, moxifloxacin, meropenem, daptomycin, etc., were administered successively. Q fever was confirmed when Coxiella burnetii(7 sequences)was detected by blood metagenomic next-generation sequencing(mNGS). During this period, SARS-CoV-2 infection was diagnosed in the patient(positive nucleic acid test on 29 May 2025). After confirmation, the treatment was adjusted to triple therapy with piperacillin-tazobactam(4.5 g q8h)combined with levofloxacin(0.5 g qd)and minocycline(100 mg q12h), alongside thoracic drainage and supportive and symptomatic treatment. Results After the triple anti-infective therapy, the patients body temperature returned to normal, but the thoracic drainage fluid remained bloody. Anti-infective therapy was continued with minocycline(100 mg q12h)combined with levofloxacin(0.5 g qd), and body temperature remained normal without any recurrence of fever. Conclusion For patients with a long-term fever and coagulopathy after the implantation of a vascular device, rare pathogens such as C. burnetii should be considered even in the absence of typical epidemiological exposure. mNGS is crucial for identifying the pathogen. Multidisciplinary management, which combining antimicrobial therapy with surgical intervention, is often essential to cure biofilm-associated infections.

Key words: Q fever, Thoracoabdominal aortic aneurysm, Post-stent implantation infection, Metagenomic next-generation sequencing