I believe the medical scientists say now that the plague is mostly transmitted by fleas (from the rats we always heard about).
Either way, these researchers are well advised to please be careful digging in a Black Death cemetery (not that it hasn’t been done before without spreading the disease, it has....but STILL......fleas are very tiny and hard to see and prevent from spreading...)
The plague carrying fleas that infected these medieval victims were already dead about the time the bodies were thrown on the cart for disposal. Fleas do not survive being buried in the ground for hundreds of years any more than the bacterium.