Crimean-Congo Hemorrhagic Fever Virus: An Emerging and Re-emerging Pathogen of Public Health Concern

Abstract

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne zoonosis distributed in Africa, Asia, Eastern Europe, and the Balkans. Humans become infected by tick-bite or from contact with infected blood or other tissues of livestock or human patients. Human infection is usually characterized by febrile illness, which can progress to a hemorrhagic state with a fatal outcome. The virus has the propensity to cause nosocomial infections, however implementation of molecular assays has facilitated rapid and safe diagnosis, especially in regions where high containment access is limited. Early diagnosis contributes toward protection of healthcare workers. The absence of any specific anti-viral treatment or approved efficacious vaccines contributes toward the public health concern regarding emergence, re-emergence, and spread of CCHFV. While the immune correlates of protection remain unclear, available data indicate that both humoral and cellular responses are required. Vaccine development has, however, in recent years been facilitated by the availability of novel animal models.

The distribution of CCHFV correlates with that of the primary vector of the virus, ticks belonging to the genus Hyalomma. The importance of the tick-vertebrate-tick cycle in maintaining CCHFV transmission is well established and sero-surveillance studies have contributed toward understanding the role of wild and domestic animals and birds as reservoirs and amplifying agents. The distribution of these ticks has, in recent years, expanded to regions where conditions are favorable for the species to establish endemnicity. Hence, there is growing concern that this virus has the potential to emerge and spread to new geographic regions.