Louping ill virus has a positive sense, single-stranded RNA genome approximately 11 kb in length. The sequencing of a complete LIV genome has revealed that it has a conserved genome structure typical of the Flaviviridae. This is divided into structural [capsid (C), pre-membrane (prM), envelope (E)] and non-structural genes (NS1, NS2A, NS2B, NS3, NS4A, NS4B, NS5). Following entry into the cell, the genome is uncoated and is directly translated into a single polypeptide which is proteolytically cleaved by a combination of host and virally encoded proteases. The envelope protein shares antigenic cross-reactivity with other members of the tick-borne flaviviruses and is the principal target of neutralizing antibodies. The virus, as with many viruses, is sensitive to heat, disinfectants and acidity.