When he was released from Emory University Hospital in October after a long, brutal fight with Ebola that nearly ended his life, Dr. Ian Crozier’s medical team thought he was cured. But less than two months later, he was back at the hospital with fading sight, intense pain and soaring pressure in his left eye.

Test results were chilling: The inside of Dr. Crozier’s eye was teeming with Ebola.