Sequencing of part of the 1D gene of foot-and-mouth disease virus was used to determine the relationships between SAT-2 viruses isolated from outbreaks which occurred in cattle in Zimbabwe and Namibia and in impala in South Africa between 1979 and 1989. The results demonstrated that the outbreaks in different countries were unrelated. Surprisingly close relationships were shown between all SAT-2 viruses isolated from cattle in Zimbabwe since 1983 but the two major epizootics which occurred in 1989 were caused by viruses which were clearly different. Conversely, two apparently unrelated outbreaks in impala in South Africa were caused by viruses which could not be distinguished.

From January 1985 to May 1991, herald strains of influenza B virus were isolated in 1987 and 1989 in Japan. In both cases, influenza epidemics caused by the same type followed in the next winter season. The HA gene sequences of the influenza B viruses isolated in Japan from 1987–91, which covers two herald waves of influenza B viruses, were analysed and located on the phylogenetic tree for influenza B viruses after the B/Singapore/64 strain. Co-circulation of at least two evolutionary lineages of the HA genes existed for influenza B viruses in Japan during the period of this study. The herald viruses in one wave (1987) were genetically close to the winter isolates and were considered to be the parental viruses for the following influenza season, while in the other wave (1989) winter isolates belonged to another lineage on which one of the herald viruses was located, but they were genetically and antigenically different from the herald viruses.