Observation of the cell cultures showed that viruses that were produced from the FMDV-SAT1 and FMDV-SAT2 co-infection caused complete CPE at 16 hpi, and that incubation with either anti-SAT1 or anti-SAT2 antisera provided partial protection, whereas incubation with both antisera provided complete protection from CPE (Supplementary Figure S2). This evidence concerns the gene SAT2 and coinfection.