They did not spread it here. All precautions were taken to ensure that.
Whether you wish to admit it or not, around 85% of those groups that have been active helping in these ebola ridden countries are faith based. How much worse would it be there if you removed them all?
That's the question. If your primary goal is to convert people, or, ahem, offer spiritual aid, you are by definition spreading more than the gospel. You are bringing together people in groups that might have had a better chance of survival if left to live their own lives.