Enveloped, spherical. Diameter possibly from 80 to 120nm.


Segmented Negative-stranded RNA linear genome, L segment is about 6.5 kb, M segment about 3.9 kb and S segment about 1.4 kb.
Encodes for at least three proteins.


The viral RNA dependent RNA polymerase (L) binds to a promoter on each encapsidated segment, and transcribes the mRNA. These are capped by L protein during synthesis using cap snatching . Transcription is terminated by a strong hairpin sequence at the end of each gene. mRNAs are capped by L protein during synthesis.



  1. Virus attaches to host receptors though glycoprotein, and is endocytosed into vesicles in the host cell.
  2. Fusion of virus membrane with the vesicle membrane; ribonucleocapsid segments are released in the cytoplasm.
  3. Transcription, viral mRNAs are capped in the cytoplasm.
  4. Replication presumably starts when enough nucleoprotein is present to encapsidate neo-synthetized antigenomes and genomes.
  5. The ribonucleocapsids buds at Golgi apparatus, releasing the virion by exocytosis.