West Nile Virus Neurologic Disease in Humans, South Africa, September 2008–May 2009

Dewald Zaayman and Marietjie Venter

Author affiliations: Author affiliations: University of Pretoria, Pretoria, South Africa (D. Zaayman, M. Venter); National Institute for Communicable Diseases, Johannesburg, South Africa (M. Venter)

Abstract

We investigated West Nile virus (WNV) as a possible disease etiology in persons hospitalized in South Africa. Of 206 specimens tested, 36 had WNV neutralizing antibodies, significantly more than in similar earlier serosurveys. Seven probable acute WNV cases were identified, suggesting WNV may be overlooked as an etiology of severe disease in South Africa.

West Nile virus (WNV), a mosquito-borne flavivirus (1), is a reemerging pathogen of global concern (2). Febrile illness occurs in ≈20% of WNV-infected persons; neurologic complications (e.g., meningitis, encephalitis, flaccid paralysis) occur in <1 a="a" href="http://wwwnc.cdc.gov/eid/article/18/12/11-1208_article.htm?s_cid=eid-gDev-email#r3" title="3">3
). Detection of IgM in serum or cerebrospinal fluid (CSF) is the preferred method for diagnosing WNV infection; however, because of cross-reactivity between flaviviruses, positive results should be confirmed by virus neutralization assay. Early WNV infection can be diagnosed by PCR and virus isolation (4), but success has been limited in diagnosing more advanced disease with these techniques.
WNV is endemic to southern Africa. In 1947, one of the largest WNV epidemics recorded occurred in the Karoo region of South Africa (5), and another occurred in combination with a Sindbis virus epidemic in 1983–84 in the Witwatersrand–Pretoria region of South Africa. The most recent seroprevalence data for WNV in the Pretoria region of South Africa is from the 1970s (reviewed in [6]). To update that information, we determined whether WNV is being overlooked as a possible cause of disease in persons hospitalized in South Africa. The University of Pretoria Research Ethics Committee approved this study.