The virus particle (1) contains a single stranded positive sense RNA. This is released (2) and translated to produce the structural (S) and non-structural (NS) proteins (3). The latter help make a negative strand copy of the genome (4) which is used as a template for the production of lots more positive strands (5). Not shown are the association of these positive strands (only) with the structural proteins to make new virus particles. Proteins are green, positive strand RNA is blue, negative strand RNA is red.