Final answer:
Viral +mRNA is synthesized in the host for translation by replication, using the viral genome as a template for the synthesis of +RNA. The newly synthesized +RNA acts like viral mRNA and can be translated by the host cell's ribosomes to produce viral proteins.
Step-by-step explanation:
If a virus has a genome consisting of negative-sense RNA, (-RNA), viral +mRNA is synthesized in the host for translation by a process called replication. The viral genome serves as the template for the synthesis of positive-sense RNA (+RNA) by viral RNA-dependent RNA polymerase (RdRP). The newly synthesized +RNA acts as viral mRNA and can be translated by the host cell's ribosomes to produce viral proteins.