Paramyxovirus

All paramyxoviruses are enveloped particles 150 to 300 nm in diameter. The tubelike, helically symmetrical nucleocapsid contains a monopartite, single-stranded, negative-sense RNA genome and an RNA-directed RNA polymerase. The nucleocapsid associates with the matrix protein (M) at the base of a double-layered lipid envelope. The spikes on the envelope contain two glycoproteins, a viral attachment protein, and a fusion protein. The paramyxoviruses can be distinguished by the gene order for the viral proteins and by the biochemical properties for their viral attachment proteins. In parainfluenza viruses, the viral protein spikes have hemagglutinating and neuraminidase activities (HN). Respiratory syncytial virus lacks both these activities and measles virus lacks neuraminidase but has hemagglutinating activity. All paramyxoviruses are labile to very labile and quickly inactivated, e.g. by heat, organic solvents, detergents, ultraviolet, or visible light, and low pH value.