Continuity mistake: In season 1 they are tracking leopards but when they take a cub for the cure it's clearly an African serval kitten.
Plot hole: How do they travel all over so quickly? Why does it take the same amount of time to travel from one continent as it does city to city? Someone in Paris talks to another in Zambia and bam, they're together all of a sudden.
Answer: In the episode "Blame It on Leo", Leo Butler, who use to work for Reiden, tells the group about the "mother cell." He explains it's Reiden's molecule vector. So it's something Reiden created. In real life science, vector cells are used to introduce DNA sequences from one organism to another. There are a variety of ways for this to occur, however, in the show not much explanation is given about how Reiden's mother cell works (and tends to bend how it works to the will of the plot).
Bishop73