Screening for Crimean-Congo Haemorrhagic Fever Virus antibodies in humans living in an endemic area of Spain.

Introduction: Crimean-Congo haemorrhagic fever (CCHF) is an emerging tick-borne viral disease. It has been described in Spain in both ticks and humans. Until July 2024 most cases have been described in the central-western part of the Iberian Peninsula. This study aims to assess the seroprevalence of antibodies against CCHF virus (CCHFV) in humans in the area that has reported the highest number of cases in Spain.

Methods: The study was conducted to estimate the seroprevalence of antibodies against CCHFV antibodies among patients referred to a hospital located in the central-western area of Spain, an endemic area for CCHFV of Spain. Patients were recruited from April 1, 2023, to June 30, 2023. A commercial ELISA was used to detect serum antibodies against the CCHFV.

Results: We screened 658 samples from 370 (56.2%) men, with a mean (±SD) age of 58.6 years (±14.3). Of these, 4 were IgG positive, representing an IgG seropositivity of 0.6% (95% CI, 0.01-1.19). None of these four patients recalled having a clinical picture that strongly suggested CCHF. Over the study period, in the population analysed in an area with circulation of CCHFV the seroprevalence of antibodies was 0.6%.

Conclusion: Our results suggest active circulation of the virus in humans in western Spain. Although the risk of developing CCHF is currently considered low, physicians should be alert to the imminent possibility of developing new cases of CCHF.