Prediction of Rift Valley fever outbreaks and impact on disease control

Global climate greatly influences local conditions that can affect vector-borne arboviral disease patterns because the viruses, their vectors, and hosts are sensitive to temperature moisture, and other ambient environmental conditions. Historical episodic outbreaks of Rift Valley fever (RVF) since the early 1950s have been associated with cyclical patterns (El Niño and La Niña) of the El Niño/Southern Oscillation (ENSO) phenomenon which results in elevated and widespread rainfall over the RVF endemic areas of Africa that produces large numbers of virus vertically infected Aedes mosquitoes and subsequent horizontally infected Culex mosquitoes. Using satellite measurements of global and regional elevated sea surface temperatures, and subsequent elevated rainfall and satellite derived-normalized difference vegetation index data, we predicted with lead times of 2.5- 4.5 months specific areas where outbreaks of RVF in humans and animals were expected and occurred in the Horn of Africa, Sudan and Southern Africa at different time periods from 2006 to 2011. Predictions were confirmed by entomological field investigations of virus activity in the areas we identified and by reported cases of RVF in human and livestock populations. This represents the first series of prospective predictions of RVF outbreaks, and this early-warning provided time for implementation of disease control response planning and mitigation.