Rift Valley Fever (RVF) is a virus (genus: Phlebovirus, family: Bunyaviridae) that primarily affects domestic livestock, but can be passed to humans. In fact, several significant outbreaks have occurred across sub-Saharan Africa and, less frequently, in places such as Egypt, Saudi Arabia, and Yemen.
Usually humans infected with the virus have either no symptoms or only a mild illness with fever, headache, muscle pain, and liver abnormalities.
In a small percentage of cases (< 2%), the illness can progress to hemorrhagic fever syndrome or meningoencephalitis (inflammation of the brain). Typically, patients recover within 2–7 days after onset, and only approximately 1% of human sufferers die of the disease.*
Among livestock, the fatality level is significantly higher. Indications of infection among livestock include vomiting and diarrhea, respiratory disease, fever, lethargy, anorexia, and sudden death in young animals. In pregnant livestock infected with RVF, virtually all pregnancies are lost.
RFV is spread by the bite of infected mosquitoes, typically from the genera Aedes or Culex.