Just to lessen to concern about the permafrost viruses. Those viruses are frozen since very long ago, and are certainly not adapted to any life as it is now on the planet or especially in the area they are found. Which also means, unlikely to infect a human just because they come in contact.
Of course viruses can adapt, but this basically has a similar risk as the bird flu jumping over to humans. Potentially even less since these viruses may not even be able to infect any lifeforms from the start.