NCIt definition : A genus of enveloped, spherical, or pleomorphic viruses with T 4 icosahedral symmetry,
in the family Togaviridae. The genome is composed of a linear, single-strand of positive
sense RNA. Alphaviruses are spread by insect vector, able to infect vertebrates and
invertebrates, and cause arthritis, encephalitis, rashes and fever in humans.;
Alternative definition : CDISC: Any viral organism that can be assigned to the genus Alphavirus.;