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Japanese encephalitis (JE) is a severe disease that is widespread throughout Asia and is spreading beyond its traditional boundaries. Three vaccines are currently in use against JE but only one is available internationally, a mouse-brain-derived inactivated vaccine first used in the 1930s. Although this vaccine has been effective in reducing the incidence of JE, it is relatively expensive and has been linked to severe allergic and neurological reactions. Cell-culture-derived inactivated and attenuated vaccines have been developed but are only used in the People's Republic of China. Other vaccines currently in various stages of development are DNA vaccines, a chimeric yellow fever-JE viral vaccine, virus-like particle vaccines and poxvirus-based vaccines. Poxvirus-based vaccines and the chimeric yellow fever-JE vaccine have been tested in Phase I clinical trials. These new vaccines have the potential to significantly reduce the impact of JE in Asia, particularly if used in an oral vaccine delivery strategy.

The sequences of the 3'-terminal 1.8 kb of the genomes of three Australian and three Welsh isolates of ryegrass mosaic rymovirus (RGMV) were determined, as too were the virion protein genes of two New Zealand isolates of RGMV. They were compared with each other and with the published sequences of a Danish and a South African isolate by distance and maximum likelihood methods, and found to be very closely related (mean nucleotide difference 5.5%). All three Australian isolates and one from North Island of New Zealand formed one consistent cluster, and the Danish and South African isolates formed another. However the relationships between these two clusters and the other isolates were not consistent; they depended on the method of comparison used, and on the protein, gene or codon position compared. Nonetheless the European (Welsh and Danish) sequences were 2-4 times more different from one another than those from the Antipodes, suggesting that the European RGMV population may be older than the Antipodean. The Danish isolate has 39 nucleotides of the 5'-terminal region of its virion protein gene frameshifted -1 relative to the 'common' sequence. Interestingly the South African isolate has a similar frameshift, but sequence comparisons indicate that this frameshift must have occurred independently; a possible example of 'convergent frameshifting'.