By Jane P. Messina, Senior Postdoctoral Epidemiologist, Department of Zoology, University of Oxford, United Kingdom.
Crimean–Congo hemorrhagic fever (CCHF) is a widespread
[citation needed] tick-borne viral disease, a zoonosis of domestic animals and wild animals, that may affect humans. The pathogenic virus, especially common in East and West Africa, is a member of the Bunyaviridae family of RNA viruses. Clinical disease is rare in infected mammals, but commonly severe in infected humans, with a 30% mortality rate. Outbreaks of illness are usually attributable to handling infected animals or people. Congo fever is usually transmitted by Hyalomma ticks.
Crimean-Congo hemorrhagic fever is found in Eastern Europe, particularly in the former Soviet Union, throughout the Mediterranean, in northwestern China, central Asia, southern Europe, Africa, the Middle East, and the Indian subcontinent.
Humans may modify the risk of CCHFV transmission through changes in land use, recreational activities, and livestock movement , and increasing awareness may also impact the incidence of CCHF , whereas limitations in diagnostic capacities and surveillance may hamper the estimation of CCHF burden in several endemic areas.
Although human cases of CCHF are relatively rare, there is no widely available safe and effective vaccine against the virus, and severe complications often lead to death. Those living or working near livestock are particularly at risk of infectious tick bites, and those working in animal slaughterhouses are at risk for exposure through infected animal blood. Human-to human transmission is also possible via exposure to infected blood and other bodily fluids, and typically occurs amongst healthcare workers or relatives who have had close contact with CCHF patients.
Ebola, Marburg and Lassa fever viruses also occur in Africa and like CCHF, pose the risk of transmission from animal reservoirs and through secondary infections in the community.We aimed to develop a candidate vaccine based on recombinant MVA expressing the CCHFv glycoproteins, to assess the induction of cellular and humoral immunity, and to evaluate efficacy in a challenge model that represents human disease.
We did this by searching through hundreds of published articles, case reports, and informal online reports of human CCHF infection since the 1950s. The compiled database can now be used alongside high-resolution environmental data (e.g., for land cover or average yearly temperatures) to identify characteristics that put certain locations at greater risk for CCHF transmission. This work is part of a wider initiative to improve understanding of the geographic distribution of important viral hemorrhagic fevers in Africa.