What the heck? How exactly are viruses supposed to remain ‘dormant’ for thousands of years in natural reservoirs? A natural reservoir is the normal host population of a virus, in which the virus persists by replicating and being transmitted from host to host. A virus can’t remain ‘dormant’ (I assume this means latent) for more than the lifetime of a single organism. And viruses do indeed evolve in their reservoirs, from which they can emerge as deadly as ever.