Viral quasi-species and recombination

Virus populations are complex ensembles of distinct but related genomes (so called quasi-species). Mathematical descriptions of viral quasi-species focus on point mutations as the principal source of variation. However, retroviruses (and many other viruses) are able to recombine their genomes. We study a mathematical model of viral quasi-species dynamics which incorporates both point mutation and recombination. We show that for low mutation rates recombination can reduce the diversity of the quasispecies and enhance overall fitness. For high mutation rates, however, recombination can push the quasi-species over the error threshold, and thereby cause a loss of all genetic information. Finally, recombination introduces bistability to the quasi-species; if the frequency of an advantageous mutant is below a certain threshold, it will not be selected.