Diagnosis of brucellosis remains challenging for several reasons, including lack of culture sensitivity, nonspecific symptomatology, and high prevalence of positive serology in endemic areas. The main objectives of this study were to identify blood biomarkers specific to brucellosis compared to other endemic infections and to monitor changes in blood biomarkers during treatment. To obtain a global profile of the disease, we employed RNA sequencing (RNAseq) of whole blood RNA to measure host response against brucellosis infection in patients from Macedonia and Spain. Long-term follow up of patients was used to classify patients as having acute or chronic/reinfection brucellosis and as treatment responders and non-responders. We observed distinct gene expression differences between samples from acute brucellosis and control donors. The magnitude of gene expression changes was associated with antibody titers determined by standard serological tests for brucellosis, including the rose Bengal and standard agglutination tests. The expression signature characteristic of acute brucellosis was also different from that of subjects with leishmaniasis. In depth integration of clinical data and serological findings with our gene expression data will be performed to provide insight into cellular and molecular mechanisms of brucellosis infection. Overall design: Whole blood from 169 subjects including 105 patients with suspected brucellosis, 17 patients with leishmaniasis, and 47 healthy controls.