title: A systematic review of Rift Valley Fever epidemiology 1931-2014.
abstract: BACKGROUND
  Rift Valley Fever (RVF) is a mosquito-borne viral zoonosis that was first isolated and characterized in 1931 in Kenya. RVF outbreaks have resulted in significant losses through human illness and deaths, high livestock abortions and deaths. This report provides an overview on epidemiology of RVF including ecology, molecular diversity spatiotemporal analysis, and predictive risk modeling.
  
  
  METHODS
  Using the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, we systematically searched for relevant RVF publications in repositories of the World Health Organization Library and Information Networks for Knowledge (WHOLIS), U.S Centers for Disease Control and Prevention (CDC), and Food and Agricultural Organization (FAO). Detailed searches were performed in Google Scholar, SpringerLink, and PubMed databases and included conference proceedings and books published from 1931 up to 31st January 2015.
  
  
  CONCLUSIONS
  A total of 84 studies were included in this review; majority (50%) reported on common human and animal risk factors that included consumption of animal products, contact with infected animals and residing in low altitude areas associated with favorable climatic and ecological conditions for vector emergence. A total of 14 (16%) of the publications described RVF progressive spatial and temporal distribution and the use of risk modeling for timely prediction of imminent outbreaks. Using distribution maps, we illustrated the gradual spread and geographical extent of disease; we also estimated the disease burden using aggregate human mortalities and cumulative outbreak periods for endemic regions.
  
  
  CONCLUSIONS
  This review outlines common risk factors for RVF infections over wider geographical areas; it also emphasizes the role of spatial models in predicting RVF enzootics. It, therefore, explains RVF epidemiological status that may be used for design of targeted surveillance and control programs in endemic countries.
authors.affiliation: Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.|Department of Public Health, Pharmacology and Toxicology, University of Nairobi, Nairobi, Kenya.|Kenya Medical Research Institute, Nairobi, Kenya; mnanyingi@kemricdc.org.
authors.forename: Mark O
authors.initials: MO
authors.lastname: Nanyingi
authors.affiliation: Centers for Disease Control and Prevention, Nairobi, Kenya.
authors.forename: Peninah
authors.initials: P
authors.lastname: Munyua
authors.affiliation: Wangari Maathai Institute for Peace and Environmental Studies, University of Nairobi, Nairobi, Kenya.
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Kiama
authors.affiliation: Department of Public Health, Pharmacology and Toxicology, University of Nairobi, Nairobi, Kenya.
authors.forename: Gerald M
authors.initials: GM
authors.lastname: Muchemi
authors.affiliation: Kenya Medical Research Institute, Nairobi, Kenya.|Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA, USA.
authors.forename: Samuel M
authors.initials: SM
authors.lastname: Thumbi
authors.affiliation: Zoonotic Disease Unit, Nairobi, Kenya.|Directorate of Veterinary Service, Nairobi, Kenya.
authors.forename: Austine O
authors.initials: AO
authors.lastname: Bitek
authors.affiliation: International Livestock Research Institute, Nairobi, Kenya.
authors.forename: Bernard
authors.initials: B
authors.lastname: Bett
authors.affiliation: Directorate of Veterinary Service, Nairobi, Kenya.
authors.forename: Reese M
authors.initials: RM
authors.lastname: Muriithi
authors.affiliation: Kenya Medical Research Institute, Nairobi, Kenya.|Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA, USA.
authors.forename: M Kariuki
authors.initials: MK
authors.lastname: Njenga
keywords: Rift Valley Fever; epidemiology; modeling; spatiotemporal