Influenza virus buds preferentially from lipid rafts (Scheiffele et al, 1999). NA protein individually accumulates at, and is selectively incorporated into rafts (Kundu et al., 1996). The signals for raft association lie within the transmembranse domain (TMD), (Barman et al., 2001, Barman et al., 2004), and raft association of NA has been shown to be essential for efficient virus replication. This is believed to be due to a requirement for a concentration of NA at specific areas of the plasma membrane to support a level of NA incorporation into budding particles sufficient to allow for efficient virus release (Barman et al., 2004).