ARS | Publication request: Forecast and Outbreak of Rift valley fever in Sudan, 2007

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 18, 2008
Publication Date: March 18, 2008
Citation: Anyamba, A., Chretien, J., Small, J., Tucker, C.J., Formenty, P., Richardson, J.H., Earhart, K., Pak, E., Britch, S.C., Schnabel, D.C., Erickson, R.L., Linthicum, K. 2008. Forecast and Outbreak of Rift valley fever in Sudan, 2007. Meeting Abstract.

Technical Abstract: Background Rift Valley fever (RVF) outbreaks occur during heavy rainfall in various sub-Saharan countries including Kenya, Somalia, and Tanzania and more recently in Saudi Arabia and Yemen. Given the wide geographic and ecological range of RVF virus, it is necessary to monitor large areas for conditions that may trigger the emergence of mosquito vectors that could spread RVF. Methods The Department of Defense Global Emerging Infections System (DoD-GEIS) coordinates epidemiologic surveillance and epidemic response through a global network of laboratories and public health professionals. In Africa/Middle East, DoD-GEIS, with NASA, also uses satellite indicators (normalized difference vegetation index [NDVI], outgoing longwave radiation [OLR], rainfall, others) to provide early warning of RVF activity. Monthly continental-scale maps flag high-risk areas. The DoD-GEIS hubs in Egypt (NAMRU-3) and Kenya (USAMRU-K) transmit RVF alerts through regional networks. Results Satellite monitoring (June-September 2007) showed focal positive NDVI anomalies and negative OLR anomalies over most of central Sudan suggested unusually heavy rainfall, and generated RVF risk warnings for central and southern Sudan in July-Septemner. In late October, RVF outbreaks were reported by WHO in humans in Sudan in White Nile, Sinnar, and Gezira states, and by early November 2007, 329 human cases, including 96 deaths were reported. The cases being reported in Gazeera State are in an area close to irrigation canals and are linked to naturally occurring cycles involving livestock and mosquitoes which are abundant in the irrigation zone. Conclusions Validated RVF forecast models may provide early warning (~3 months) for RVF epidemics in Africa. Model performance, integrated with epidemiologic and environmental surveillance systems, should be assessed systematically for RVF and other mosquito-borne diseases using historical epidemiologic and satellite data.