Sorry, not impressed. Two vectors, fleabite is established and verified. The second is a different strain and hypothetical. When the strain changes, the characteristics of the disease chance, in particular it can become too lethal or nonlethal.
“The second is a different strain and hypothetical.”
There is nothing “hypothetical” about it at all. It is demonstrated by the forensic evidence retrieved from the corpses of the victims it infected and killed in historical times. The research shows the genetic mechanism which produces the more virulent form/s. The particular genetic changes are of a simple type and location which can be expected to reoccur from time to time. These particular changes disable and/or circumvent the human immune system and are therefore not going to be prevented by vaccines or inherited immune responses from prior exposures to the bactria. Because the disease does tend to kill the hosts so rapidly, it does not generally have an opportunity to adapt to an immune system it is already circumventing, so it does die off to a great extent; but it does not die off before killing off a plurality of the total human population during its occurrence. Bottomline, this pathogen is a clear danger to Human health in its occasional form as a pneumonic plague.