ABSTRACT
The togaviruses are a heterogeneous group of viruses which have some common morphological and physicochemical properties. Visualization of togaviruses by negative stain electron microscopy has not been satisfactory because particles tend to appear nondescript. The Flaviviridae comprises the former group B arboviruses which were formerly members of the Togaviridae. Particles are 40 to 50 nm in diameter which is somewhat smaller than the range for togaviruses. Elongated forms of Togaviruses may also be seen budding from the surface of infected cells. Togaviruses and Flaviviruses are positive strand RNA viruses which multiply in the cytoplasm of infected cells. Flaviviruses are usually seen in cytoplasmic vacuoles and are probably released through canaliculi connecting the endoplasmic reticulum with the plasma membrane or perhaps the cellular secretory mechanism. The genera of Togaviridae which are medically important include: Alphavirus and Rubivirus. All species of Alphavirus multiply in arthropods as well as in vertebrates.
