The concept of promoter and enhancer function during replication has been introduced recently in relation to the flavivirus CREs (16) . The promoter has been identified as a complex of highly conserved interacting RNA structures recruited from the 5 0 -and 3 0 -UTR to assemble viral and cellular proteins into a functional RdRp complex. In evolutionary terms, the 3 0 -UTR of the TBFV group is formed by four conserved long imperfectly repeated sequences (LSRs), genetic remnants of which are revealed in the MBFV, NKV and PABV groups (17) . It has been proposed that the 5 0 -UTR may have evolved from a trans-terminal duplication of the archival flavivirus 3 0 -UTR (16) .