“there is a risk of the pathogen returning via leaching of soil in a cemetery”
Umm, we are talking about a virus that requires a host to survive, not the Terminator.
Viruses don't "survive". If the virion isn't damaged, it must be able to 1) infect a cell 2) successfully replicate in the cell. Clearly, the bodies involved here are capable of providing a protected environment for virions to remain undamaged. Samples kept in a lab are often placed into cryogenic storage to prevent degradation. There is no host there.