This is the catalytic subunit of the viral RNA-dependent RNA polymerase complex. This complex is involved in viral RNA replication that produces (+)-stranded genomes via a complementary, (-)-stranded intermediate. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Part of the viral RNA-dependent RNA polymerase complex, the other subunits are probably the host ribosomal protein S1, EF-Tu and EF-Ts.