Could you let me know the difference in term of meaning
- Ebola is spreading very fast.
- Ebola has spread.
Does it mean that in the first sentence it is a ongoing action In the second sentence the action is completed?
It is indeed an ongoing action.
In this context, it does look like a completed action, because it's presented as a past action which is supposed to have consequences on the present.
However, it could be completely different if we added something else behind.
Here, the "since" indicates it's been happening since some point in time, suggesting it's not over yet. So it is still an ongoing action in this case.
Bonus:
We don't know if the action is completed or not: all we know is that it's been happening continuously between two points in time (possibly until now).