How do we distinguish the term "Virtue" from "altruism"?

How do we distinguish the term "Virtue" from "altruism"? what is their difference?
It seems confusing, altruism is something understand generally in terms of behavior, but virtue (a hypernym) seems to encompass altruism (the hyponym) and altruistic behavior, yet virtue has something more to it, something in addition to it being altruistic conduct.