The pathogenic and clinical characteristics of community-acquired and hospital-acquired co-infection in patients hospitalized with severe fever with thrombocytopenia syndrome

Background Co-infection can accelerate the progression of SFTS, this study aims to analyze the clinical characteristics of SFTS-associated co-infection and identify the associated risk factors. Methods In this retrospective study, we analyzed epidemiology, pathogen distribution patterns, and laboratory findings between community-acquired infections (CAIs) and hospital-acquired infections (HAIs) in SFTS patients. Our objectives were to determine the prevalence, characterize clinical manifestations, and identify potential risk factors associated with SFTS co-infection. Results Among 231 SFTS patients, 81 (35.1%) had co-infection. SFTS patients with CAIs exhibited the highest mortality rate (23.4%). Compared to those without co-infection, patients with CAIs had more severe clinical presentation and poorer outcome. Antifungal treatment significantly improved survival in SFTS with CAIs-related fungal infections, but had no benefit in those with HAIs-related fungal infections. Pulmonary infections were associated with reduced survival time in SFTS patients with HAIs but had no significant impact on those with CAIs. Multivariate logistic regression analysis identified several independent risk factors for CAIs in SFTS patients, including diarrhea, cerebral infarction, antifungal therapy, ICU admission, elevated D-Dimer levels, and A/G <1.05. Among SFTS patients with co-infection, A/G <1.05 demonstrated potential predictive value for CAIs (AUC = 0.714, 95% CI: 0.626-0.832). Further analysis revealed that an A/G ratio <1.05 indicated moderate discriminatory performance for SFTS patients with CAIs related pulmonary fungal infections (AUC = 0.799, 95% CI: 0.702-0.896). Conclusions SFTS patients with CAIs had poorer clinical outcomes than patients without co-infection or those with HAIs. An A/G ratio <1.05 may serve as a supportive marker for identifying patients at increased risk of CAIs and could assist clinical risk stratification.