Fleas are interesting insects with a prominent place in history. The adults of some species can transmit the plague (Yersinia pestis), which was responsible for the deaths of millions of people. In 1347, the first cases of the plague known as the Black Death appeared in Europe, and the disease was well established in 1348. The plague was so infectious that whole towns ceased to exist and fleeing people spread the disease far and wide. Before the end of the outbreak, about a third of the population of Europe was dead; this is the highest percentage of a population ever killed by an epidemic. The Black Death was so devastating that there were not enough people left in some areas to bury the dead. In 1664 and 1665, the plague returned to London, killing 100,000 people. In 1892 it spread to China and India killing up to six million people. San Francisco had an outbreak in 1904 that left 122 people dead.
There are many species of fleas and they infest many species of mammals and some birds.
There are many species of fleas throughout North America, but the ones considered pests most often are dog fleas (Ctenocephalides canis) and cat fleas (Ctenocephalides felis), as these species will infest homes. Other species carry plague and other diseases, but they will not infest a home in large numbers. Dog and cat fleas prefer parts of the country that are humid.
A flea can jump a distance of 150 times its own body length, which would be the equivalent of a human doing a standing broad jump of a quarter mile.