When "cholera" is in the title of the novel, you figure it's got to be pretty important. As it turns out, it is. Cholera breaks out all over the place in this novel. It's a periodic threat, a cause for exodus (Fermina's family moves to the city while fleeing a cholera epidemic), a cause of death (Dr. Urbino's father dies of cholera), and a constant fear. As such, it motivates a lot of the novel's action.
More than that, cholera is always being associated with love, and not just in the title. As we discover when Florentino falls ill time and time again due to pains of the heart, the "symptoms of love are the same as those of cholera" (2.25). If cholera can be interpreted as a symbol of love in the novel, what does it say about the characters that Dr. Urbino's relationship with the disease is one of purposeful and systematic eradication, while Florentino's is one of suffering?