New York, July 19: Researchers have found evidence of long-term Ebola viral persistence in rhesus monkeys who have survived the infections caused by the deadly disease and no longer show symptoms.

The findings demonstrated persistent Ebola virus replication in the eye, brain and testes of animals -- the same sites where Ebola has been found to persist in humans.

In the eye, the virus was found in macrophages that contain the protein CD68 in their surface which could be where the virus "hides", the researchers said.

"In the animals that showed an acute or shortened course of disease, the virus primarily replicated in the blood vessels," said Xiankun Zeng, doctoral student from the US Army Medical Research Institute of Infectious Diseases (USAMRIID).

"In those with a longer disease progression, the virus spread to surrounding tissues in the immune privileged sites. And in the survivors, we could see that the virus had migrated out of the blood vessels and into specific locations within immune privileged sites," Zeng added.

The study, published in the journal Nature Microbiology, also showed that Ebola virus persists in the brain by breaking down the blood-brain barrier and causing inflammation.

The 2013-2016 Ebola virus outbreak in West Africa was the most widespread and rapidly became the deadliest occurrence of the disease since its discovery in 1976.

"This study lays the foundation for developing animal models of persistent Ebola virus infection in humans," Zeng explained.

"What we observed in primates is quite similar to what happened during the outbreak--there were survivors with latent infection, but the virus was not detectable in the blood. This makes it much more difficult to contain the spread of the virus."

Ebola virus persists in monkeys