Who knew? People are still dying of the plague in the United States. That’s right. The scourge of Europe of the middle ages is still an endemic disease in modern day America. So far this year there have been 4 deaths attributed to the black death from 15 infections. Okay, so it isn’t millions of corpses lining the streets like in the good old days but it’s still a surprise.
The problem seems to be that the causative pathogen, the bacteria Yersinia pestis, and the fleas that carry it are happily living on prairie dogs and ferrets and other animal based carriers. This natural reservoir of disease means that it is extremely difficult to eradicate as you would also have to cure (or kill) every animal as well as every person that was infected. One of the factors that made it easier to wipe out smallpox was that there was no animal reservoir for the pathogen to hide away in, once you had vaccinated every human there was no where else for it to go and it went extinct. This is also the case for polio.
The matter is complicated further by the fact that one of those main reservoir species, the black footed ferret, is critically endangered and there are substantial efforts being made to raise its numbers in the wild. Concurrently with that, then, the United States Geological Survey and the United States Fish and Wildlife Service are working on vaccinating the wild populations they’re trying to nurture.
It’s a bit of a Catch 22, then; we want to revive the biodiversity of the south western US but we also want to try and stop people getting all gangrenous and dead. A thorny problem but one we can crack.