They created models to compare the likelihood of the disease being spread by rats, airborne transmission and fleas and lice on humans and clothes.
Researchers found that seven of the nine cases showed that there was a closer resemblance between the human model and the outbreak compared to the other two potential factors.
Scientists said: “While it is commonly assumed that rats and their fleas spread plague during the Second Pandemic there is little historical and archaeological support for such a claim.
"Here, we show that human ectoparasites, like body lice and human fleas, might be more likely than rats to have caused the rapidly developing epidemics in pre-Industrial Europe."
The plague was wiped out of Britain in 1666 but in some parts of the world it still remains prevalent. The three most endemic countries are Madagascar, the Democratic Republic of Congo and Peru.
The findings were published in the Proceedings of National Academy of Science.
