Emergencies preparedness, response

Rift Valley fever


Cattle herd drinking water in a Dambo during a RVF outbreak in Kenya 2007.

Rift Valley fever (RVF) is a viral zoonosis that was first identified in Kenya in 1931. This mosquito-borne disease primarily affects animals but that also has the capacity to infect humans. The vast majority of human infections result from direct or indirect contact with the blood or organs of infected animals. Such contact may occur during the care or slaughtering of infected animals or possibly from the ingestion of raw milk. Human infection can also result from the bites of infected mosquitoes.

While most human cases are relatively mild, a small percentage of patients develop a much more severe form of the disease that appears as one or more of three distinct syndromes: ocular disease, meningoencephalitis and viral haemorrhagic fever. For the most severs cases, the predominant treatment is general supportive therapy.

RVF outbreaks in East Africa are closely associated with periods of heavy rainfall that occurs during the warm phase of the El Niño/Southern Oscillation (ENSO) phenomenon. These findings have enabled the successful development of forecasting models and early warning systems for RVF using satellite images and weather/climate forecasting data enabling authorities to implement measures to avert impending epidemics. RVF risk maps updated monthly are edited by the US Global Emerging Infections Surveillance and Response System (DoD-GEIS).

Contact information

Department of Pandemic and Epidemic Diseases
World Health Organization
Avenue Appia 20
1211 Geneva 27