[Epidemiology and Risk Factors of Crimean-Congo Hemorrhagic Fever: Ankara Province 2011-2023]

Crimean-Congo hemorrhagic fever (CCHF) is a common tick-borne viral disease caused by viruses belonging to the genus Orthonairovirus in the family Nairoviridae and order Bunyaviridae. The aim of this study was to determine the clinical characteristics, risk factors and mortality of patients diagnosed with CCHF who were followed up and treated in Ankara or referred from external centers between January 1, 2011 and December 31, 2023. Patients who met the definitive case definition of CCHF and were followed up through the CCHF web-based information system of the Provincial Health Directorate between January 1, 2011 and December 31, 2023 were investigated retrospectively. The patients' sociodemographic and clinical characteristics, physical examination and laboratory findings, posteroanterior chest X-ray findings, treatments given, epidemiological history, CCHF IgM and CCHF IgG measured by Enzyme Linked Immunosorbent Assay for CCHF virus in blood or body fluids sent to a reference laboratory with the diagnosis of CCHF, CCHF virus RNA results of the first and second samples studied by reverse transcription polymerase chain reaction (RT-PCR), survival and death results were recorded. A total of 329 confirmed CCHF cases followed in Ankara province were included in the study. 40.4% of the cases were resident in Ankara and were infected within Ankara province and 59.6% were infected outside Ankara province. The median age of CCHF cases was 48 (minimum= 2-maximum= 86), 58.1% were male and 41.9% were female. 35.9% were farmers and livestock breeders, 1.2% were healthcare workers and 62.9% were in other occupational groups. 82.05% of CCHF cases had a history of tick bite. The highest number of CCHF cases was seen in July. The most common symptoms in CCHF cases were fatigue (92.7%), fever (82.1%) and widespread body pain (72.6%), and the most common physical examination findings were fever above 38 °C (63.5%), tachycardia (10.6%) and vaginal bleeding (11.2%). The most common laboratory findings were thrombocytopenia (86.6%), elevated aspartate aminotransferase (AST)/alanine aminotransferase (ALT) (80.5%), and leukopenia (70.8%). The CCHF case fatality rate was found to be 7.3%. In our study, most patients with CCHF were belonged to other occupational groups, reported a history of tick bites, presented with nonspecific symptoms and had thrombocytopenia, elevated AST/ALT and leukopenia. Age, impaired consciousness, gastrointestinal bleeding, and an INR value above 1.2 were factors that increased the risk of death in CCHF cases. Therefore, considering our study findings, we believe that CCHF can be considered in cases with nonspecific symptoms, thrombocytopenia, elevated AST/ALT and leukopenia, enabling early diagnosis, rapid initiation of treatment, identification of the need for intensive care, and reduction of transmission. Furthermore, factors that increase the risk of death, such as age, impaired consciousness, gastrointestinal bleeding and an INR value above 1.2, should be considered in CCHF case management.