Viral Recombination

Some cells may be infected by two different strains of a virus at the same time causing a mix-up of both genetic sequences in a process called viral recombination. More specifically, after the virus has entered the cell's cytoplasm, they disassemble and begin to replicate their genomes.

Similar regions of each genome can pair together and exchange pieces, reconnecting the strands. Alternatively, the viruses can swap some of their segments in a process called reassortment, in which new viruses made inside the cell can have a mixture of the strains, such as half of their segments from strain one and the other half from strain two.

These newly formed viruses have now evolved from the two original viruses forming populations that may continue to change over time.