Evaluation of epidemiological characteristics of Crimean-Congo haemorrhagic fever patients reported to the National Surveillance System in Türkiye, 2011-2024.

Crimean-Congo haemorrhagic fever (CCHF) is a major public health concern in Türkiye, which has the highest global incidence. This study analysed national surveillance data from 2011 to 2024 to describe the epidemiology of CCHF and identify predictors of fatality through a retrospective cohort analysis using the CCHF Information System. All laboratory-confirmed cases reported between 2011 and 2024 were included. Descriptive statistics summarized demographic, clinical, and laboratory variables. Logistic regression was applied to determine fatality predictors, and adjusted odds ratios (ORadj) with 95 % confidence intervals (CI) were calculated. Among 27,269 samples tested, 11,811 cases were laboratory-confirmed, of which 552 died (case fatality rate: 4.7 %). Males comprised 60.5 % of cases, and the mean age was 46.8 ± 18.5 years. Tick-bite or tick contact (62.2 %) and close contact with animal blood or tissues (69.6 %) were common exposure histories. Fatality was independently associated with increasing age (ORadj: 1.034; 95 % CI: 1.029-1.040), male sex (ORadj: 1.3; 95 % CI: 1.1-1.6), splenomegaly (ORadj: 2.0; 95 % CI: 1.5-2.7), haemorrhagic findings (ORadj: 2.4; 95 % CI: 2.0-3.0), platelet count <20,000/mm³ (ORadj: 10.3; 95 % CI: 6.7-15.7), platelet count 20,000-49,000/mm³ (ORadj: 4.6; 95 % CI: 3.0-7.0), and elevated AST or ALT (ORadj: 1.5; 95 % CI: 1.1-2.0). Patients who did not receive ribavirin had higher fatality (ORadj: 1.5; 95 % CI: 1.2-2.0). Although Türkiye reports many cases, fatality remains comparatively low. Identified predictors can support early risk stratification and clinical management. Strengthening surveillance, laboratory capacity, and clinician training may further reduce mortality.