There are probably thousands (and my guess would be much more) viruses that that dance on the information playground that is our genome, metagenome, and the genomes of the organisms we host. Fighting a few of them is probably not going to be a significant issue.
Having more individuals around by itself would also lead to mutations which the environment may select for in the future. By itself there is no such thing as a beneficial mutation (gene import) unless the environment proves it to be.