The Ebola virus can linger in bodily tissues even after the person appears to have made a full recovery, according to experts.

Parts of the body such as the eye, central nervous system and testes can harbour the virus, which can also behave in an unpredictable way.

John Edmunds, from the London School of Hygiene and Tropical Medicine, said: “The Ebola virus can occasionally persist for some months in certain tissues within survivors.

“The risk of transmission from these individuals appears to be very low. However, with so many survivors in West Africa now, there is a risk that further outbreaks can be triggered, which is why authorities have to remain very vigilant.”

Ben Neuman, a virologist at the University of Reading, told BBC Radio Scotland he believes the outlook for Pauline Cafferkey is good.

It’s surprising and we’re just learning how to deal with this

He told the Good Morning Scotland programme: “The nice news here is that she’s beaten the virus once so she can probably beat it again.

“The odds are that she actually has inherited a lucky set of genes and these are probably what protected her the first time and probably what will keep her safe the second time, regardless of any treatment. I think the outlook’s good.”

He said scientists are still learning about the virus and its effects.

“It seems that some of the ongoing health problems with people’s eyes, joints and hair loss are actually caused not by the after-effects of Ebola, but by the small amounts of Ebola which are still residing somewhere in the body,” he said.

“It’s surprising and we’re just learning how to deal with this.”

Neuman said the aim of any treatment for Cafferkey would be to try to eliminate any last traces of the virus.

He told BBC Radio Scotland: “The good news is that it’s probably not going to be infectious. The virus, when it is removed from the blood once, tends to retreat into the hard-to-access compartments of the body.

“It will hide in places like the back of your eye, in breastmilk, places like that. But we also have some treatments now that are actually shown to work and reduce complications from Ebola, and that’s due to brave people like Nurse Cafferkey.”

Julian Hiscox, professor of infection and global health at the University of Liverpool, said: “We know that Ebola virus can shelter in the body in what are called immune pri-vileged sites such as the eye, central nervous system and testes.

“Due to the sheer scale of this outbreak compared to previous ones, we are going to see aspects of Ebola virus infection that we have not observed before.

“I think the persistence of the virus in asymptomatic individuals is a potential reservoir of the virus. We know that infectious virus is present in semen for a number of months. It’s why men who have had Ebola and recovered are advised to abstain or wear condoms.”

The return of the Ebola virus in Scottish nurse Pauline Cafferkey is “concerning”, a leading expert has said.

Virologist professor Andrew Easton, of Warwick University, said that although the virus had persisted in a patient before, it was unusual so long after the first diagnosis.

He said: “We haven’t seen it return after this long. It is concerning. There are lots of unknowns at this stage. It is very difficult to tell and I don’t want to predict what the outcome may be.”

It has resurfaced from where it has been residing in the past 10 months

Ebola can occasionally persist for some months in certain tissues within survivors as it is retained by parts of the body where the immune system struggles to reach. These include the testes and the liquid in the back of the eye.

Easton said Cafferkey’s condition may have worsened as the virus pushes back from where it was contained – meaning she would go through the same stages of the virus as she had previously.

He said: “It has resurfaced from where it has been residing in the past 10 months, which will push the process into its normal stages again.”

Easton added that Cafferkey could face experimental drugs.

He added: “Even basic medical provisions have shown to improve survival rates. There are lots of new treatments that could be used.

“The usual protocol of testing these drugs is being put to the side because the patient is at such risk. It is up to the highly-trained medical staff who understand the risk to decide whether to use them.”

Easton said it was “unlikely” the 58 people identified as being in contact with Cafferkey before she was diagnosed would be affected.

Facts and figures about virus

What is Ebola?

Ebola is one of the world’s deadliest diseases, with more than 50 per cent of cases resulting in death. The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission. Outbreaks mainly occur in remote villages in Central and West Africa.

Fruit bats of the Pteropodidae family are believed to be the natural host of the virus. The disease was first recorded in two simultaneous outbreaks in 1976 near the Ebola River in the Democratic Republic of Congo.

How did the latest outbreak occur?

The first cases of the current outbreak in West Africa were detected in March 2014. It is the largest and most complex Ebola outbreak since the Ebola virus was first discovered. The most severely-affected countries are Guinea, Liberia and Sierra Leone, where weak health systems and recent instability have contributed to the spread of the virus. The World Health Organisation declared the West Africa outbreak a Public Health Emergency of International Concern. For those living outside West Africa the threat level remains very low.

What are symptoms?

The symptoms of Ebola are severe, with patients often overcome by a sudden onset of fever as well as weakness, muscle pain and headaches. Vomiting, diarrhoea, rashes, kidney and liver problems follow as the virus grips the body. The incubation period – the time between infection and the onset of symptoms – ranges from two days to three weeks.

How is it spread?

Ebola spreads from person to person as a result of direct contact with the blood, organs or other bodily fluids of those infected, with healthcare workers among those most at risk. However, it is only contagious while an infected person is suffering from symptoms.

How is it treated?

Patients diagnosed with Ebola are placed in isolation in intensive care, where their blood oxygen levels and blood pressure are maintained at the right level and their body organs supported.

How many have died?

As of October 4, 2015, 11,312 people have died globally after contracting Ebola. This includes a number of tourists and travellers in Europe and America after returning from West Africa.

For the first time last week, no new cases of Ebola were reported, the World Health Organisation said.

Is there a vaccine?

There is currently no licensed treatment or vaccine for Ebola virus disease, although potential new vaccines and drug therapies are being developed and tested. Both MIL 77 and ZMapp are experimental treatments which have been used to treat patients.