[JBW1949]

I thought it has long been known that fleas were the cause...

[gundog]

Me, too.

[ProtectOurFreedom]

That was my understanding, too. Seems that this article says the fleas jumped person to person (or via crappy “bedding” and infested clothes) rather than traveling on rats. The fleas probably weren’t fussy about how they got around as long as a meal was waiting.

The bigger question is how or why the bacterium Yersinia pestis carried by the fleas turned so nasty.

[mass55th]

"I thought it has long been known that fleas were the cause..."

That's what I've always heard. The rats were the carriers.

[sparklite2]

I thought so, too.

[Phillyred]

Same. The rats were just the carriers of the fleas.