Clinical features of Q fever confirmed by plasma metagenomic next-generation sequencing.

BACKGROUND: The clinical features of acute Q fever and their link to transient autoantibodies remain poorly defined. We characterized 44 plasma mNGS-confirmed cases and identified predictors of prolonged fever. METHODS: Retrospective study (2021-2026) of 44 patients with confirmed Q fever (mNGS + clinical + exposure criteria). Patients were grouped by post-treatment fever duration (>7 days vs. ≤7 days). RESULTS: Cohort was predominantly middle-aged (median 52.5 years) and male (95.5%). Common presentations: fever (95.5%), headache (45.5%), pulmonary involvement (51.2%). Elevated CRP (97.7%) and ESR (90.9%) were universal. Transient antiphospholipid antibodies (78.9%, all negative at 12 weeks) and ANA (23.5%) were frequent. Prolonged fever (>7 days) was associated with higher WBC, CRP, ESR, lower CD8+ and B cells, and aPL positivity (all p<0.05). CONCLUSIONS: Acute Q fever frequently induces transient autoantibodies. Prolonged fever correlates with an inflammatory and lymphopenic phenotype, underscoring immune dysregulation in recovery.