Maximum-likelihood trees of the (a) S-fragment and (b) VP1 coding sequences of the analysed FMDVs. The trees (1000 bootstrap replicates) were optimized using the heuristic nearest-neighbour-interchange method as implemented by the software program MEGA (version 5.10). All the sequences of the FMDV O/SEA/Mya-98 lineage present in East Asia during 2009–2011 are included, as well as other FMDV sequences including those from other serotypes in which a similar deletion in the S-fragment has been found (isolates in bold). Bootstraps values < 70% are not shown. Sequences represented by names in lower case are derived from cell culture isolates generated from field strains (C3/Resende/BRA/1955, C/UK/149/1934, A2/Spain/43), A/Canefa/ARG/1/1961 and A25/BA/Argentina/1959).