Epidemiology and Infection

Original Papers

Human and animal viruses/Q fever

Genetic relationship in southern African Crimean-Congo haemorrhagic fever virus isolates: evidence for occurrence of reassortment

F. J. BURTa1 c1, J. T. PAWESKAa2, B. ASHKETTLEa3 and R. SWANEPOELa2

a1 Department of Medical Virology, National Health Laboratory Services Universitas and Faculty of Health Science, University of the Free State, Bloemfontein, South Africa

a2 Special Pathogens Unit, National Institute for Communicable Diseases, Sandringham, Johannesburg, South Africa

a3 Department of Medical Virology, Faculty of Health Science, University of the Free State, Bloemfontein, South Africa

SUMMARY

Crimean-Congo haemorrhagic fever (CCHF) is a tick-borne viral zoonosis widely distributed in Africa, Asia and eastern Europe. Reassortment of CCHF genome segments has been shown to occur in nature. We therefore investigated the genetic relationship of southern African isolates using partial sequence data for each RNA segment, S, M and L, and comparing the tree topologies constructed using a neighbour joining method. A total of 21 southern African isolates were studied. The incongruencies which were identified in S, M and L sequence datasets involved group switching implying reassortment for 15 isolates. A higher fatality rate occurred in patients infected with isolates which had apparently acquired M segments from a group in which predominantly Asian strains are usually found. This suggests that reassortment may affect the pathogenicity of the virus.

(Accepted December 03 2008)

(Online publication January 23 2009)

Correspondence:

c1 Author for correspondence: Professor F. J. Burt, Department of Medical Virology, National Health Laboratory Services Universitas and Faculty of Health Science, University of the Free State, Bloemfontein, South Africa. (Email: burtfj.md@ufs.ac.za)

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