Translation of mRNA by the ribosome is essential for all life. It’s normally exceptionally accurate, with spontaneous error rates of only ~1 in 100,000 codons.

When RNA viruses infect cells, they use the ribosomes in the host cell to translate their genomes. However, they often force the ribosome to make 'mistakes' - e.g. shift into a different reading frame, initiate in a different place, or read through a stop codon. 

These ‘forced errors’ are actually tightly-regulated events that are vitally important to viral gene expression. If disrupted, many viruses fail to complete their replication cycles. We're trying to better understand these events at a molecular level.