Epidemiology of Crimean-Congo Hemorrhagic Fever (CCHF) in Africa-Underestimated for Decades

Abstract

Crimean-Congo hemorrhagic fever (CCHF) is endemic in Africa, but the epidemiology remains to be defined. Using a broad database search, we reviewed the literature to better define CCHF evidence in Africa. We used a One Health approach to define the impact of CCHF by reviewing case reports, human and animal serology, and records of CCHF virus (CCHFV) isolations (1956-mid-2020). In addition, published and unpublished collection data were used to estimate the geographic distribution of Hyalomma ticks and infection vectors. We implemented a previously proposed classification scheme for organizing countries into five categories by the level of evidence. From January 1, 1956 to July 25, 2020, 494 CCHF cases (115 lethal) were reported in Africa. Since 2000, nine countries (Kenya, Mali, Mozambique, Nigeria, Senegal, Sierra Leone, South Sudan, Sudan, and Tunisia) have reported their first CCHF cases. Nineteen countries reported CCHF cases and were assigned level 1 or level 2 based on maturity of their surveillance system. Thirty countries with evidence of CCHFV circulation in the absence of CCHF cases were assigned level 3 or level 4. Twelve countries for which no data were available were assigned level 5. The goal of this review is to inform international organizations, local governments, and healthcare professionals about shortcomings in CCHF surveillance in Africa to assist in a movement toward strengthening policy to improve CCHF surveillance.

Figure 1.

Evidence of CCHF in Africa using a One Health approach. The following level classification is applied: level 1, CCHF cases reported annually through established surveillance; level 2, CCHF cases reported intermittently in absence of robust surveillance; level 3, no CCHF cases reported and no robust surveillance established, but available data point toward the possibility of undetected/unreported CCHF cases (animal/human serology, CCHFV detected in Hyalomma ticks); level 4, no CCHF cases reported and no robust surveillance or epidemiologic/epizootiologic studies, but Hyalomma ticks present; and level 5, no available data. Classification at the country level was performed for policy implications. Country boundaries do not necessarily reflect the geographic area at risk and are not necessarily endorsed by the authors. The map was created using ArcGIS Release 10.61. Source: Database of Global Administrative Areas. This figure appears in color at www.ajtmh.org.