Faculty of Health Sciences
School of Medicine
Department of Medical Virology
Pathogenesis and diagnosis of West Nile virus in South Africa
West Nile virus (WNV), a mosquito-borne Flavivirus, is widely distributed in Africa, Asia and Europe and North America. Recent outbreaks in the northern hemisphere have been charactirised by relatively high rates of potentially fatal neurological complications, especially in elderly human patients, birds and horses. In Southern Africa, WNV is widely endemic, and human infections tend to be sporadic, with large epidemics occurring only when unusually high rainfall or hot weather favours breeding of the mosquito vectors. Five-fifteen cases are reported per annum although only a proportion of suspected cases are subjected to laboratory investigation. A few cases of severe disease have been recognized, including fatal hepatitis and non-fatal encephalitis in humans, and fatal encephalitis in a horse and a dog. Two phylogenetic lineages exist, lineage 1 found in the Northern hemisphere and Australia, while lineage 2 found only in Southern Africa and Madagascar. Comparison of the phylogenetic relationships and neuroinvasiveness in mice indicated that pathogenicity is genotype specific and not related to lineage or geographic distiution. We suspect that WNV associated meningitis and encephalitis is largely missed in South Africa because of a preceived idea that WNV is not a cause of serious disease. We are investigating the molecular biology of neuroinvasive lineage II WNV strains and the host immunity that play a role in protection and pathogenesis. We further aim to determine the extent of neurological cases in South Africa. Other projects include development of molecular and immunological tools for improved diagnosis, and characterisation of related zoonotic Flavi viruses, and virus discovery projects as well as recombinant vaccines
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