Excellent question, and idea!!!
Even though they survive, they are seriously weakened by the disease. Many that survive are crippled, have diet changes, etc. Just read Lazamataz thread on the effects of Ebola.
Also, the blood tranfustion conversation goes like this:
"Hello patient, I am Doctor ________ here with good news and bad news. The good news is that we will be giving you blood transfusion from an Ebola survivor and should help you defeat the virus before your body is wrecked or you melt.
The BAD news is that you will have malaria, HEP C, and HIV afterwards.
Your choice: Take the blood and probably live for another decade or more, or dont, and you'll be dead in a week".