The relatively compact nature of the flavivirus genome, together with constraints imposed by the need to replicate in vertebrate and invertebrate hosts, means that additional CRE sequences may be present in parts of the genome other than the non-coding regions. Indeed, RNA secondary structures have been predicted within the coding region of several flaviviruses (26) (27) (28) . Here, using bioinformatic and reverse genetic analysis we demonstrate that the capsid-encoding region of TBEV contains an REE which we designate SL6 (26, 27) . Phylogenetic evidence suggests that the MBFV group also contains at least a partial SL6-like structure, though it is absent in the NKV or PABV groups. The significance of these findings in the context of flavivirus evolution and adaptation to transmission is discussed.