Ebola (or ebola hemorrhagic fever) is a zoonotic viral disease which has resurfaced multiple times in separate "spillover" events from its animal reservoir species, which likely includes bats and nonhuman primates. There's more than one ebolavirus, and multiple strains have been implicated in outbreaks, with the Zaire ebolavirus thus far being the most deadly.

Even though ebola can be transmitted from one human to another, humans are not a reservoir species for ebolavirus due to the fact that it a) does not remain indefinitely latent in the human body b) is relatively hard to transmit in that it requires direct physical exposure to infected material and c) it is very frequently fatal. This is why outbreaks have been relatively sporadic with no global spread.