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United States Department of Agriculture

Agricultural Research Service

Title: Forecast and Validation of the Rift Valley fever outbreak in East Africa: 2006-2007

item Chretien, Jean-Paul - DOD-GEIS
item Small, Jennifer - NASA-SPACE FLIGHT GODDARD
item Tucker, Compton - NASA-SPACE FLIGHT GODDARD
item Formenty, Pierre - BDP/CDS/EPR/WHO
item Richardson, Jason - USAMRU - KENYA
item Britch, Seth
item Schnabel, David - USAMRU - KENYA
item Erickson, Ralph - DOD-GEIS
item Hightower, Allen - CDC-KEMRI - KENYA
item Breiman, Robert - CDC-KEMRI - KENYA
item Linthicum, Kenneth

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., Pak, E., Britch, S.C., Schnabel, D.C., Erickson, R.L., Hightower, A., Breiman, R., Linthicum, K. 2008. Forecast and Validation of the Rift Valley fever outbreak in East Africa: 2006-2007. Meeting Abstract.

Technical Abstract: Background The instantaneous occurrence of El Nino / Southern Oscillation (ENSO) warm events and anomalous warming of the equatorial western Indian Ocean (WIO) are associated with elevated and widespread rainfall over East Africa. Such, sustained, heavy rainfall in East is associated with the emergence of large populations of virus infected Aedes spp mosquitoes and the Rift Valley fever (RVF) outbreaks. Methods The Department of Defense Global Emerging Infections System (DoD-GEIS) collaborating with NASA Goddard Space Flight Center, operate an near-real time environmental monitoring and RVF risk mapping system for Africa/Middle East, DoD-GEIS. Using a combination of sea surface temperature [SST], outgoing longwave radiation [OLR], rainfall, and satellite derived normalized difference vegetation index [NDVI] to map areas conducive to the emergence of RVF-mosquito vectors. Results The development of warm ENSO conditions with anomalous warming of SSTs in the central and eastern Pacific (CEP) region and the concurrent anomalous warming of SSTs in the WIO region during the September – November 2006 period enhanced rainfall over the oceans and East Africa. The excess moisture resulted in anomalous growth and green-up in vegetation, creating ideal ecological conditions for the emergence of virus-infected mosquitoes. Using a RVF monitoring and risk mapping algorithm the December 2006-May 2007 RVF outbreak in, the Horn of Africa region was forecast as early as September 2006 A mapping of human case locations shows that 64% of the cases were reported in areas mapped to be at risk within the RVF potential epizootic area. Conclusions The ability to monitor key climate indicators, including SSTs in the CEP and WIO regions and rainfall and NDVI over the Horn of Africa, enabled prospective warning of a RVF outbreak and enabled a regional-level assessment of RVF risk that was critical in guiding early entomological investigations and control activities.

Last Modified: 11/27/2015