Seroprevalence of Crimean-Congo hemorrhagic fever in humans in the world health organization European region: A systematic review

Background: Crimean-Congo hemorrhagic fever (CCHF) is an emerging infectious disease caused by a Nairovirus. CCHF is a tick-borne disease that is predominantly associated with Hyalomma ticks and have a widespread distribution in Africa, Asia and Europe. CCHF usually presents as a subclinical disease, but in some cases, it may present as a hemorrhagic fever with a high mortality rate. This systematic review of the literature was performed to identify the available evidence on the prevalence of CCHF in the European Region of the World Health Organization, based on seroprevalence (IgG antibodies). Methodology: A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement protocol. PubMed, Embase, and the Web of Science were used for the search (up to January 31, 2019), combining the following MeSH terms: [“Crimean-Congo haemorrhagic fever” OR “Crimean-Congo hemorrhagic fever virus” OR “Congo-Crimea” OR “Crimea-Congo”] AND [“Europe”] AND [“epidemiology” OR “seroprevalence”]. The abstracts were screened. Subsequently, full-text articles were selected and reviewed based on the PICOS (Population-Intervention-Comparison-Outcomes-Study type) criteria by two independent reviewers for inclusion in the final analysis. The data were qualitatively synthesized without quantitative pooling due to the heterogeneity in the study populations and methodologies. Principal findings: Twenty-eight articles (9 from western Europe, 18 from central Europe and 3 from eastern Europe) were included in the analysis. All articles were cross-sectional studies (descriptive studies). Conclusions: The highest seroprevalence of CCHF is found in central and eastern European countries. Southern and western Europe countries, such as Greece and Spain, have low levels of endemicity, but the spread of the infection, which is associated with climate change, is a possibility that we should keep in mind. Further studies, especially larger seroprevalence studies in humans and animals, are needed to establish the current status of the CCHF epidemiology and to generate standardized guidelines for action in the region. Author summary: Crimean Congo hemorrhagic fever (CCHF) is a widespread tick-borne viral disease caused by a Nairovirus of the Bunyaviridae family. CCHF-virus (CCHFV) has been considered to be one of the eight priority emergent pathogens for the last 3 years by the World Health Organization (WHO), requiring urgent attention in Research, Development and Innovation (R&D&I) because of its epidemic potential in the near future In this systematic review, we aimed to describe the epidemiological impact of CCHFV (seroprevalence for IgG antibodies and the associated risk factors) in the WHO European Region (WHO/Europe). In this systematic review suggests the following conclusions. i) The highest values of CCHFV seroprevalence are found in Turkey, the Russian Federation, and Kazakhstan. ii) Greece has a high seroprevalence, though only one death associated with CCHFV has been reported. This fact contrasts with the neighboring countries, such as Balkan countries and Turkey, where the rate of severe infections seems to be higher. iii) Extensive studies should be developed in European countries to establish the actual epidemiological situation and to take additional preventive measures for the future.