Rift Valley fever virus. In this micrograph virions are seen budding into membrane vesicles (Golgi vesicles) in the cytoplasm of a liver cell (hepatocyte) of an infected rat. The 100 nm (nanometer) virions then make their way to the cell surface and are released. This virus replicates to very high concentrations very quickly and causes very rapid damage to the liver and other organs. The virus is mosquito-borne and in nature affects sheep, cattle, wild mammals and humans. The virus was the cause of one of the most explosive epidemics ever seen when it appeared in 1977 in Egypt. A recent epidemic in Saudi Arabia and Yemen represents the first time that the virus has appeared outside Africa. This virus, because it can infect many different vertebrates and many different mosquitoes, presents perhaps the greatest potential threat posed by any virus. Magnification approximately x30,000.
Micrograph from F. A. Murphy, University of Texas Medical Branch, Galveston, Texas.