Venter, MarietjieHuman, StaceyZaayman, DewaldGerdes, Gertruida HermannaWilliams, June HeatherSteyl, Johan Christian AbrahamLeman, Patricia A.Paweska, Janusz TadeuszSetzkorn, HildegardRous, GavinMurray, SueParker, RissaDonnellan, Cynthia Mary BridgetSwanepoel, Robert2009-09-102009-09-102009-05-06Venter, M, Human, S, Zaayman, D, Gerdes, GH, Williams, J, Steyl, J, Leman, PA, Paweska, JT, Setzkorn, H, Rous, G, Murray, S, Parker, R, Donnellan, C, Swanepoel, R 2009, 'Lineage 2 West Nile virus as cause of fatal neurologic disease in horses, South Africa', Emerging Infectious Diseases, vol. 15, no. 6, pp. 877-884. [www.cdc.gov/eid]1080-605910.3201/eid1506.081515http://hdl.handle.net/2263/11203Serologic evidence suggests that West Nile virus (WNV) is widely distributed in horses in Southern Africa. However, because few neurologic cases have been reported, endemic lineage 2 strains were postulated to be non-pathogenic in horses. Recent evidence suggests that highly neuroinvasive lineage 2 strains exist in humans and mice. To determine whether neurologic cases are being missed in Southern Africa, we tested 80 serum or brain specimens from horses with unexplained fever (n = 48) and/or neurologic signs (n = 32) for WNV. From March 2007 through June 2008, using reverse transcription-PCR (RT-PCR) and immunoglobulin (Ig) M ELISA, we found WNV RNA or IgM in 7/32 horses with acute neurologic disease; 5 horses died or were euthanized. In 5/7 horses, no other pathogen was detected. DNA sequencing for all 5 RT-PCR-positive cases showed the virus belonged to lineage 2. WNV lineage 2 may cause neurologic disease in horses in southern AfricaenCoordinating Center for Infectious Diseases, Centers for Disease Control and PreventionWest Nile virus (WNV)Horse (Equus caballus)Lineage 2Reverse transcription polymerase chain reaction (RT-PCR)Neurologic diseaseSouthern AfricaArticle