Oriental rat fleas, Xenopsylla cheopis, can carry the coccobacillus Yersinia pestis.
The infected fleas feed on rodent vectors of this bacterium, such as the black rat, Rattus rattus, and then infect human populations with the plague, as has happened repeatedly from ancient times, as in the Plague of Justinian in 541–542.
 Outbreaks killed up to 200 million people across Europe between 1346 and 1671.
The Black Death pandemic between 1346 and 1353 likely killed over a third of the population of Europe.

Because fleas carry plague, they have seen service as a biological weapon.
During World War II, the Japanese army dropped fleas infested with Y. pestis in China.
The bubonic and septicaemic plagues are the most probable form of the plague that would spread as a result of a bioterrorism attack that used fleas as a vector.
Oriental rat fleas, Xenopsylla cheopis, can carry the coccobacillus Yersinia pestis. The infected fleas feed on rodent vectors of this bacterium, such as the black rat, Rattus rattus, and then infect human populations with the plague, as has happened repeatedly from ancient times, as in the Plague of Justinian in 541–542.  Outbreaks killed up to 200 million people across Europe between 1346 and 1671. The Black Death pandemic between 1346 and 1353 likely killed over a third of the population of Europe.
Because fleas carry plague, they have seen service as a biological weapon. During World War II, the Japanese army dropped fleas infested with Y. pestis in China. The bubonic and septicaemic plagues are the most probable form of the plague that would spread as a result of a bioterrorism attack that used fleas as a vector.
Flea