Rift Valley fever virus particle,computer artwork. This virus particle consists of an RNA (ribonucleic acid) genome enclosed in a protein capsid (yellow),which is itself surrounded by a glycoprotein envelope (orange). Rift Valley fever occurs in Africa,infecting humans,cattle,sheep,rodents and other species. It is transmitted by insects,mainly mosquitoes,and causes chills,fever,a headache and joint and muscle pain. It is rarely fatal,but can cause retinal haemorrhages that may lead to visual impairment |