Originally Posted by Kraxis
Yes, it can and will transer from human to human. There was an outbreak in India a few years ago. It got pretty scary for a while (had an epidemic in the making) until enough penicillin and vaccines got sent in.
The bubonic plague can indeed infect from person to person, you would just need any bodily fluid. And it wasn't as if people were exactly clean or even stayed clear of the sick (besides the lepers), so person to person transfers does not seem too far out.
Anyway, the rat theory is getting a lot of flak these days. Quite simply the rats didn't and don't move about very much, and their fleas while able to spread the plague would die after the first bite on humans, so they couldn't really jump back to new rats or other humans.
If it truly had been the rats then we would have seen a much more different pattern than the rather linear advance. We would have seen outbreaks quite soon after the first in Italy in the big Med. ports, creeping around to the Atlantic. Possibly reaching England a few months after the first outbreak. Now that didn't happen... Instead the plague slowly pushed upwards from the landside.
I do not hope that anybody would argue that rats were relatively rare on ships. Or that new rats were transported aboard whenever (mostly) new cargo got lifted on.