FOREIGN GENE INTEGRATION. “It has long been appreciated that viral sequences can become integrated in the genome of their host, either as part of their normal replication cycle or accidently through host-encoded reverse transcription and/or recombination activities. Such integration of viral DNA, when it occurs in the germ cell lineage, can lead to the vertical transmission and fixation of viral sequences in the host population.”
https://www.sciencedirect.com/science/article/pii/S0959437X17301685