Rift Valley Fever

Rift Valley fever is a viral disease affecting both humans and livestock, most often causing a short illness of fever, muscle pain and headache lasting about a week. In a minority of cases it becomes severe, causing loss of sight beginning about three weeks after infection, brain infections with severe headache and confusion, or bleeding with liver problems within the first few days, and the bleeding form carries a death rate as high as 50 percent. The virus spreads mainly through mosquito bites or contact with the blood or tissue of infected animals such as cattle, sheep, goats and camels, and outbreaks have occurred only in Africa and Arabia, usually after unusually heavy rain increases mosquito numbers. The disease was first reported among livestock in Kenya's Rift Valley in the early 1900s, and the virus was isolated in 1931.