“Given that the disease is blood-borne and not many people get bitten by fleas, an outbreak like you describe is impossible.”
Evidently you failed to read the references at the provided links, especially the prior FreeRepublic Post #30 and its source:
The Mutant Genes Behind the Black Death
Quanta Magazine ^ | 10/6/15 | Carrie Arnold
Posted on ;PM by LibWhacker
http://www.freerepublic.com/focus/f-chat/3346880/posts
Example:
[Quote]
“We found the very earliest state at which Yersinia pestis could cause respiratory disease. And as soon as it had pla, it could grow rapidly and cause pneumonia,” Lathem said.
Y. pestis didn’t just acquire pla; the bacterium also changed it. A chance mutation altered one amino acid in pla, which greatly increased its virulence by allowing the bacterium to penetrate more deeply into the body. Once there, it could make more copies of itself, making it more likely to be transmitted to another person, whether by coughing or by fleabite.
The findings change how researchers think about pneumonic plague. The ability to cause pneumonia was thought to have been a last-minute addition to the deadly repertoire of Y. pestis. Lathem’s work suggests that Y. pestis acquired pla, and thus the ability to cause pneumonia, very early. The mutation in pla happened later, transforming a bacterium capable of causing localized outbreaks of disease into the mass killer we know today.
“Our work is pointing to this mutation in pla as one of these Big Bang events in plague,” Lathem said. “It was already ready to cause severe pneumonia, and once it could cause invasive disease, everything could amplify.”
Plague continues to spread, although improvements in pest control, hygiene and antibiotics have dramatically decreased the size of outbreaks and the number of people who die from them. Yet the DNA of these bacteria carries the chilling reminder that the next major pandemic may be only a few mutations away.
{Unquote]
Every so often this bacterium undergoes a genetic change which turns on its ability to become a respiratory disease or pneumonic plague as opposed to only a blood borne disease. Once the disease becomes a pneumonic plague and it becomes capable of disabling the normal immune system defenses, it becomes very highly contagious through coughing, skin to skin contact, and other airborne means in a day and age when present day intercontinental transportation systems virtually guarantee transmission to the global population before the disease has any hope of being quarantined. The likelihood of a planeload of passengers being infected by the air recirculated through the aircraft cabin is very high.
While the difficulty in eliminating the disease throughout Nature is highly problematical, so is the death toll from the pneumonic and some other virulent forms of the disease which wipe out major fractions of the human population whenever they undergo the same genetic changes we see have happened before and certainly will happen again.
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.