	The negative sense RNA genome is in three segments. The L segment encodes the L endonuclease (an RNA-dependent RNA polymerase enzyme) for genome replication and mRNA synthesis. The M segment encodes a polyprotein, further cleaved in the Gn and Gc surface glycoproteins for attachment and the NSm nonstructural protein that influences virulence. The S segment encodes the NSs protein for immune suppression and virulence, and the N structural nucleocapsid protein.