Genome analysis of influenza C viruses isolated in 1981/82 from pigs in China.

The genomes of influenza C viruses isolated from pigs in Beijing, China during 1981/82 and of human influenza C virus strains isolated between 1947 and 1981 were analysed by comparison of RNA migration patterns on gels and by two-dimensional oligonucleotide (ON) mapping. The genomes of the pig isolates were closely related to one another, though in part distinguishable by point mutations. They were similar to but more distantly related to the genomes of human influenza C viruses. The genome of the C/pig/Beijing/10/81 isolate differed from that of the C/pig/Beijing/32/81 isolate obtained on the same day at the same place by a number of mutations which were all located in RNA segments 1 and 2 as shown by ON mapping. This result suggests that the two isolates are genetically related by a reassortment event which is likely to have occurred in nature. The question whether or not pigs are a natural reservoir for human influenza C viruses cannot be answered at present.