Hidden threats: Brucellosis diagnosis and co-infection patterns in Crimean-Congo Hemorrhagic Fever suspects

•The study determined the prevalence of brucellosis in patients with a preliminary diagnosis of CCHF to be 3.2%.•Clinical symptoms and demographic data of patients with CCHF and brucellosis co-infection were analyzed.•Significant differences in laboratory findings were found between patients with CCHF and brucellosis co-infection and those diagnosed only with brucellosis, particularly in fibrinogen levels and creatine kinase levels.•It was emphasized that brucellosis should be considered early in the differential diagnosis in patients suspected of having CCHF.•No fatalities were observed among the participants, indicating that brucellosis does not increase mortality in CCHF patients. This study aims to investigate the frequency of brucellosis in patients with Crimean-Congo Hemorrhagic Fever (CCHF). In this study, 1231 patients were evaluated retrospectively, including 14 patients with CCHF and brucellosis coinfection and 25 patients with brucellosis alone. Statistical methods such as the Mann-Whitney U test and Fisher's exact test were used. Of the patients with a preliminary diagnosis of Crimean-Congo Hemorrhagic Fever (CCHF), 3.2% were found to have brucellosis. In the group co-infected with brucellosis and CCHF, the time to hospital admission was shorter. Additionally, tick exposure and headache were observed more frequently in this group. Creatine kinase levels were found to be higher in the co-infected group, while lymphocyte counts and fibrinogen levels were lower compared to the group with brucellosis alone. Our study revealed a 3.2% rate of brucellosis in patients with a preliminary diagnosis of CCHF. Due to the similarity of symptoms and common risk factors, the differential diagnosis of brucellosis should be considered in patients diagnosed with CCHF. Additionally, the possibility of brucellosis coexisting with CCHF should always be considered. Even in patients diagnosed with CCHF, an evaluation for brucellosis must be conducted.