Note that there was a human flea, but it's extinct. The fleas you might actually find on a human are dog fleas.

The human flea is not extinct and is actually one of the counter examples as it does infect other species such as pigs.

Humans cannot host infestations of dog fleas. You can be bitten by a dog flea, but you cannot complete it's life cycle. If you find yourself constantly dealing with fleas, you are in the presence of an active infestation from another animal.