“The last thing I can remember,” Crozier says “is going into the back doors at Emory from the ambulance.”

Crozier was in the ICU biocontainment unit for 40 days. His kidneys and lungs failed. He was put on dialysis and a ventilator and given experimental drugs. He even received plasma from another Ebola survivor.

“If you had told me on day one that a week later I would develop what we call multi-system organ failure — brain failure, respiratory failure, kidney failure — and asked me to predict my survival, it probably would have been zero,” Crozier said.

When, in October, he walked out of Emory University seemingly free of Ebola, it shocked the medical community.

But little did anyone know, the virus was still there – hiding in one of his eyes.

Soon after, Crozier developed severe inflammation in his left eye. In December they sampled the fluid inside of it, and found that the virus was there “at very high levels.”

The levels of Ebola in his eye weren’t just “high” – they were 10 times the level that was once in his blood. The virus even changed the color of his eye, from blue to green.

Doctors think that the active virus remained in Crozier’s eye, undetected because the human eye is a “sanctuary” site. In the human body, sites such as the eyes, semen and central nervous system are believed to be “immune-privileged,” protected from the collateral damage to bodily tissue that can occur when the immune system is fighting infection.

Previously, it was unknown whether the virus could hijack immune-privileged sites. Crozier described the discovery as a “canary in a coal mine."

Doctors from the U.S. and Liberia are now undertaking a study, examining the long-term health effects of Ebola virus disease on 7,500 people, including 1,500 Ebola survivors and 6,000 of their close contacts. In an interview with America Tonight, NIAID Director Anthony S. Fauci said that in addition to long term health effects, the study will look at symptoms of Ebola survivors and determine if any are "associated with a hiding of the virus in a very secluded place, like the eye or the semen or even in the central nervous system."