title: Anomalous High Rainfall and Soil Saturation as Combined Risk Indicator of Rift Valley Fever Outbreaks, South Africa, 2008-2011.
abstract: Rift Valley fever (RVF), a zoonotic vectorborne viral disease, causes loss of life among humans and livestock and an adverse effect on the economy of affected countries. Vaccination is the most effective way to protect livestock; however, during protracted interepidemic periods, farmers discontinue vaccination, which leads to loss of herd immunity and heavy losses of livestock when subsequent outbreaks occur. Retrospective analysis of the 2008-2011 RVF epidemics in South Africa revealed a pattern of continuous and widespread seasonal rainfall causing substantial soil saturation followed by explicit rainfall events that flooded dambos (seasonally flooded depressions), triggering outbreaks of disease. Incorporation of rainfall and soil saturation data into a prediction model for major outbreaks of RVF resulted in the correctly identified risk in nearly 90% of instances at least 1 month before outbreaks occurred; all indications are that irrigation is of major importance in the remaining 10% of outbreaks.
authors.forename: Roy
authors.initials: R
authors.lastname: Williams
authors.forename: Johan
authors.initials: J
authors.lastname: Malherbe
authors.forename: Harold
authors.initials: H
authors.lastname: Weepener
authors.forename: Phelix
authors.initials: P
authors.lastname: Majiwa
authors.forename: Robert
authors.initials: R
authors.lastname: Swanepoel
mesh_terms: D000818:Animals; D009033:Culicidae / Q000821:virology; D004196:Disease Outbreaks; D062306:Geography, Medical; D049674:History, 21st Century; D006801:Humans; D058751:Livestock; D015233:Models, Statistical; D011891:Rain; D012189:Retrospective Studies; D012295:Rift Valley Fever / Q000453:epidemiology* / Q000266:history / Q000635:transmission; D012296:Rift Valley fever virus; D012306:Risk; D012621:Seasons; D012987:Soil; D013019:South Africa / Q000453:epidemiology; D015047:Zoonoses
chemical_list: D012987:Soil
keywords: Rift Valley fever; South Africa; epidemics; epizootics; forecasting; herd immunity; livestock; mosquito vectors; mosquitoes; outbreaks; prediction models; rainfall; risk indicator; soil saturation; vaccination; vector-borne infections; viruses; zoonoses