Six months after the Ebola virus ravaged West Africa and dominated headlines around the world, experts are facing another challenge: thousands of survivors are now experiencing a mysterious set of symptoms persisting long after their recovery, including vision loss and joint and muscle pain.

Doctors are calling it Post-Ebola Syndrome, and the phenomenon is still not very well understood — partly because in the past, the disease's high fatality rate has meant there haven't been too many survivors.

But this latest outbreak — which so far has seen more than 26,000 reported cases on the African continent and killed almost 11,000 people — has left us with the largest number of Ebola survivors in history.

Sierra Leone health workers look for people suffering from Ebola symptoms. Cases of the disease are still being reported in Sierra Leone and Guinea. (Michael Duff/Associated Press) "This is a massive outbreak compared to anything we've ever had before...so a much bigger group both to try to take care of and also to try to understand the various problems that they face," says Dr. Daniel Bausch, a senior consultant for the World Health Organization's clinical team on pandemic and epidemic diseases. Part of his work involves organizing the WHO's Ebola survivor support network.

Some of the most common problems they're seeing in patients include muscle and joint pain, fatigue, hearing loss, vision problems and an inflammation of the eye called uveitis, persisting months and even years after they are first infected.

"We even have reports of people who are treated who progress to full blindness," Bausch says. "These are not small problems."

Virus lingers in the body

There are other viruses known to leave persisting symptoms long after recovery, such as parvovirus, which can cause joint pain, and chikungunya, which can lead to severe arthritis. But "Ebola has some specifics that we haven't seen," says Bausch.

A health worker checks the temperature of a girl at the entrance to a Red Cross facility in the town of Koidu, Kono district, in Eastern Sierra Leone. (Baz Ratner/Reuters) Medical experts are finding that Ebola virus can linger in some areas of the body where the immune system is slow to destroy invaders. One is the testes, and people are advised to avoid semen from male survivors

Mysteriously, the virus has also been found inside a survivor's eyeballs. A paper in the May issue of the New England Journal of Medicine outlines the case of Dr. Ian Crozier, an American doctor who contracted Ebola while volunteering in Sierra Leone. While treating him for eye inflammation weeks after he was discharged from hospital, doctors were surprised to discover the virus was still present in his left eye.

While anecdotal evidence of Post-Ebola Syndrome is mounting, WHO is still trying to conduct proper research in order to better understand how the virus is affecting survivors.

"One of the challenges with these things of course is that unless you systematically collect data...It can be hard to compare this group of survivors in one village and another group of survivors in a different area," says Bausch.

Survivors face stigmatization, PTSD

Along with these medical symptoms, Ebola survivors also face lasting psychological and social consequences.

"We're seeing levels of post-traumatic stress syndrome and depression ... not just among the survivors themselves, but also families," says Dr. Adi Nadimpalli, the medical co-ordinator for a survivors' clinic the Liberian capital of Monrovia, which is run by Medecins Sans Frontieres.

Kumba Fayah, 11, recovered from the Ebola virus and lives with her extended family in Liberia. (Jerome Delay/Associated Press) He says many survivors have had family members or people close to them die in the outbreak, and now they are struggling to cope with the losses. At the clinic in Monrovia, there are survivor-run groups to help provide support.

"There is also a huge problem with social issues, like stigmatization, community acceptance," Nadimpalli says. The stigmatization can be so strong that some survivors lose their jobs or are forced to leave their communities.

"It's a challenge to get patients through the immediate aftermath of Ebola," he says. "Even a year later, some people are experiencing these problems."

The scale of this outbreak was really something beyond our capacity and is still challenging our capacity. – Dr. Daniel Bausch, WHO consultant

Providing medical care and support to the thousands of Ebola survivors across West Africa is daunting, especially in a region where resources and trained personnel are scarce. For example, Bausch points out that the entire country of Sierra Leone, with a population of six million people, has only two trained ophthalmologists and one practising psychologist.

"The scale of this outbreak was really something beyond our capacity and is still challenging our capacity," he says. "Now we have thousands of survivors who need care. We need to develop a system for that."

Compounding the problem is that the outbreak is still not over — cases of Ebola are still being reported in Sierra Leone and Guinea — so whatever resources are available are still needed to fight the spread.

"It's sort of like putting out 99 per cent of a forest fire. If you don't get it all and you turn your back, not only does one ember still burn, but it threatens to come back into a larger fire," Bausch says.

He adds that even with other diseases like MERS now dominating the headlines, he hopes the public won't be complacent about Ebola. "We need to support people in West Africa and make sure we get to zero for this outbreak, and keep giving people the care that they need for survivors and try to help rebuild."