Researchers thought the bacterium would infect fleas on rats, and when the rats died, the fleas would jump to humans, infecting them. Rats are also thought to be responsible for spreading more recent ...

It turned out that human fleas weren’t good at spreading the bacteria. Next, Hinnebusch and his team turned their attention to body lice. The researchers conducted a series of laboratory ...

and fleas sometimes infect humans through bites; thus, fleas and rats are thought to be the primary drivers of plague pandemics. "Body lice - which feed on human blood - can also carry Y.