Risk Factors for Co-Infections in Patients With Severe Fever With Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging viral hemorrhagic fever with a high fatality rate and notable public health impact, caused by a novel phlebovirus, primarily transmitted through infected tick bites. This study aimed to assess the prevalence of co-infections among hospitalized patients with SFTS, characterize isolated pathogens, and evaluate demographics, clinical features, and laboratory variations to identify potential risk factors for co-infections. In a cohort of 78 SFTS patients categorized into co-infection and non-co-infection groups, 44.9% (35/78) experienced co-infections, with a 25.7% mortality rate in that subgroup. Pulmonary and bloodstream infections, particularly fungal infections, were most common, and earlier onset of co-infections correlated with higher fatality. Univariable logistic regression identified significant risk factors, followed by multivariable analysis to determine independent predictors. Changes in mental status, hemorrhage, deep venous or arterial catheterization, mechanical ventilation, activated partial thromboplastin time (APTT) > 55 s, albumin < 37.5 g/L, interleukin-6 > 18.700 pg/mL, and interleukin-10 > 21.300 pg/mL emerged as significant risk factors, with hemorrhagic symptoms and low albumin remaining independent predictors. Internal validation through bootstrap resampling yielded a mean area under the receiver operating characteristic curve of 0.795 (95% CI: 0.706-0.868). These findings suggest that early recognition of these predictors may improve co-infection management in SFTS patients, leading to better clinical outcomes and more informed clinical decisions.