<P> Yersinia pestis circulates in animal reservoirs , particularly in rodents , in the natural foci of infection found on all continents except Australia . The natural foci of plague are situated in a broad belt in the tropical and sub-tropical latitudes and the warmer parts of the temperate latitudes around the globe , between the parallels 55 degrees North and 40 degrees South . Contrary to popular belief , rats did not directly start the spread of the bubonic plague . It is mainly a disease in the fleas ( Xenopsylla cheopis ) that infested the rats , making the rats themselves the first victims of the plague . Infection in a human occurs when a person is bitten by a flea that has been infected by biting a rodent that itself has been infected by the bite of a flea carrying the disease . The bacteria multiply inside the flea , sticking together to form a plug that blocks its stomach and causes it to starve . The flea then bites a host and continues to feed , even though it can not quell its hunger , and consequently the flea vomits blood tainted with the bacteria back into the bite wound . The bubonic plague bacterium then infects a new person and the flea eventually dies from starvation . Serious outbreaks of plague are usually started by other disease outbreaks in rodents , or a rise in the rodent population . </P>
<P> Yersinia pestis circulates in animal reservoirs , particularly in rodents , in the natural foci of infection found on all continents except Australia . The natural foci of plague are situated in a broad belt in the tropical and sub-tropical latitudes and the warmer parts of the temperate latitudes around the globe , between the parallels 55 degrees North and 40 degrees South . Contrary to popular belief , rats did not directly start the spread of the bubonic plague . It is mainly a disease in the fleas ( Xenopsylla cheopis ) that infested the rats , making the rats themselves the first victims of the plague . Infection in a human occurs when a person is bitten by a flea that has been infected by biting a rodent that itself has been infected by the bite of a flea carrying the disease . The bacteria multiply inside the flea , sticking together to form a plug that blocks its stomach and causes it to starve . The flea then bites a host and continues to feed , even though it can not quell its hunger , and consequently the flea vomits blood tainted with the bacteria back into the bite wound . The bubonic plague bacterium then infects a new person and the flea eventually dies from starvation . Serious outbreaks of plague are usually started by other disease outbreaks in rodents , or a rise in the rodent population . </P>
what was the vector of the bubonic plague
what was the vector of the bubonic plague
fleas
fleas