The great filter argument is that there is no intelligent life in the universe because as soon as it gets intelligent enough to dominate, "fate" wipes it out. Arguing that fossil diseases can fulfill this task is to argue against evolution and technology - these are diseases that didn't wipe us out backintheday and now that we have several hundred years of epidemiology under our belts, it's unlikely that we'll suffer at the hands of a bug that petered out.

The two human diseases mentioned - smallpox and anthrax - are also mentioned in the place that has done the most weaponization of both: Russia. Smallpox vaccine is over two hundred years old by now and some tens or hundreds of thousands of healthcare workers and soldiers are already vaccinated. Anthrax, for its part, is perhaps the most domesticated bioweapon in anyone's arsenal and regardless of the thawing permafrost, this is permafrost we're talking about: no one is concerned about a sudden outbreak in Edmonton, they're worried about something drifting downriver from the hinterlands.

It's a vexing problem to be sure, and another ancillary problem caused by global warming, but if I were to pick "likely sources of global pandemics for $500" alex, "permafrost" wouldn't be high on my list.