n.
Any of a group of viruses that are agents of influenza and can cause the common cold , mumps , and measles in humans, canine distemper , rinderpest in cattle, and Newcastle disease in fowl.
The virus particle is encased in a fatty membrane, variable in shape from spheroidal to threadlike, and studded with spikelike protein projections; it contains RNA . These viruses react with a protein on the surface of red blood cells; many of them cause red blood cells to clump together.