A British nurse, thought to have made a full recovery in January from Ebola, has been taken to a hospital in a serious condition due to what health officials described as delayed complications from the virus — raising questions about the long-term impact of the disease on survivors.

The Telegraph reported that 39-year-old Pauline Cafferkey, who contracted the virus in Sierra Leone, was in an isolation unit at the Royal Free Hospital in London early on Friday morning. The hospital said in a statement that she was suffering from "an unusual late complication" of Ebola and is in serious condition, but did not offer more details.

Cafferkey is one of several survivors who have reported suffering from issues that appear to be related to lingering effects of the virus.

A year ago, when the World Health Organization sent a team to Kenema, a part of Sierra Leone where the outbreak first hit, patients reported a whole range of "post-Ebola syndrome" symptoms.

"Apart from visual problems which affect approximately 50% of Ebola survivors in Kenema, people complain of 'body aches' such as joint, muscle and chest pain. They also suffer headaches and extreme fatigue, making it difficult to take up their former lives — especially if it involved manual work — as farmers, labourers and housewives," the World Health Organization  said in a report.

Margaret Nanyonga, a psychosocial support officer for the WHO in Kenema, was quoted by the organization as saying that she was seeing a lot of people with vision problems. “Some complain of clouded vision, but for others the visual loss is progressive. I have seen 2 people who are now blind," Nanyonga said.

The most studied case may be that of American doctor Ian Crozier, who was treated for Ebola at Emory Hospital in Atlanta in September 2014 after becoming infected in Sierra Leone.

According to a case study published in the New England Journal of Medicine in June, Crozier left the hospital in October with no signs of Ebola in his blood but developed inflammation and very high blood pressure in his left eye two months later. An ophthalmologist tested the fluid in his eye and found incredibly high levels of the virus — even higher than had been at his blood. In addition to causing swelling and vision problems, the virus is also believed to have turned his eye from blue to green.

"It was a shocking finding," his doctors said.

In a video released by Emory University, Crozier described the ordeal. Specialists treated him with corticosteroids which he said may have saved his vision.

"The likely thing is that I'm an outlier. Until we know more we don't know whether other West African survivors will have virus in their eyes," Crozier said.

Nina Pham, a nurse in Dallas who contracted the virus from a patient she cared for at Texas Health Presbyterian Hospital, has said that she is suffering  from myriad health problems. In an interview with The Dallas Morning News, she described symptoms of fatigue, insomnia, body aches and liver problems and said she is " frightened by the unknown possible long-term effects of Ebola and experimental treatments used to save her life." Pham is suing the owner of the hospital for negligence that caused the conditions that led to her infection.

Infectious disease experts said that while it's possible the virus may linger in some patients, they believe it is unlikely the virus could be transmitted by survivors.

Crozier and the Emory doctors said they were careful with infection control procedures after they made the discovery but believed that there was no chance of him passing on the infection without people coming into direct contact with the fluid in his eyes.

In the case of Cafferkey, British health authorities said they were reaching out to those who had been in contact with the nurse as a precaution but said that they believe "the risk to the general public remains low."

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