If rats don't travel, then how do they spread the plague? If they do travel, then quarantine would not work. If they travel with humans, then we would expect to

If rats don't travel, then how do they spread the plague? If they do travel, then quarantine would not work. If they travel with humans, then we would expect to see massively higher infection and death rates among travellers due to prolonged times with infected rats as they dragged them everywhere (where is this evidence?) The plague spread across Europe at an enormously fast rate (some believe that hemorrhagic fever with a separate bubonic outbreak in Italy).