Analysis of the VP8* subunit of VP4 of the outbreak samples revealed two conserved amino acid substitutions at positions 237 (Ser-Leu) and 242 (Thr-Ser) when compared to the previously circulating strains. NSP4, the rotavirus enterotoxin, was also analysed. Conserved amino acid changes were observed in the 2007 outbreak G9P[8] strains. All changes were located in the cytoplasmic

domain that has numerous overlapping functional domains. In particular, the amino acid changes at positions 137 and 168 resulted in changes of the polarity, these alteration may have a functional impact on the maturation process of the virus [32]. There are find more six described G9 VP7 lineages, Lineage I contains strains isolated in the 1980s in the USA and Japan and Lineage II contains asymptomatic neonatal strains from India [33]. Lineage III contains strains currently circulating globally including the G9 VP7 gene of the 2007 Alice Springs outbreak strains which clustered 26s Proteasome structure into sub-lineage D [33]. Four lineages of P[8] VP4 genes have been described [34]. The 2007 Alice Springs outbreak strain clustered within P[8] Lineage 3 which contains

G9P[8] and G1P[8] human strain in current global circulation. Nine enterotoxin genogroups have been described for NSP4, the 2007 Alice Springs outbreak strains clustered within enterotoxin genogroup 1 with the other characterised Australia isolates. All three genes analysed clustered closely with a 2008 G9P[8] isolate from the USA, and the VP7 gene clustered with a 2005 G9P[8] Brazil isolate. Thus sequence analysis demonstrates that

the Alice Springs 2007 outbreak strain was caused by a single G9P[8] strain, more similar to strains isolated in the USA and Brazil than CYTH4 to previously detected Australian isolates. The gastroenteritis outbreak occurred between March and July 2007, and during this period 173 children were admitted to Alice Springs Hospital. Seventy-eight patients had confirmed rotavirus infection. Ninety-two percent of hospitalisations involved Indigenous children and 74% involved children from remote communities [35]. A good vaccine efficacy of Rotarix against G9P[8] strains was observed. Vaccine efficacy for two doses against all hospitalisations for gastroenteritis was 77.7% and for confirmed cases of rotavirus gastroenteritis was 84.5% [35]. These results were similar to Rotarix™ vaccine efficacy against G9P[8] strains in a European trial, 85% and 83.76% from the pooled data of the phase II and III clinical trials [12] and [36]. In Brazil where 63% of disease caused by G9 strains, 80% protective efficacy has been demonstrated [37]. This outbreak occurred just 6 months after vaccine introduction, and this is highly unlikely to have influenced virus or genotype selection. However, vaccine introduction is expected to influence the genetic evolution of rotavirus strains over time.