Latent reservoirs are super interesting. They've seen in experiments that they keep copies of all of the HIV strains that infected people go through (HIV is one of the viruses with the highest mutation rates). When people have gone off meds sometimes they've managed to sample their blood and seen how all of this viral strains activate around the same time.
To be clear, I imagine that it’s not that the reservoir is literally “intentionally” storing different strains but just that viruses are more accurately thought of as “quasispecies swarms”:
