The Ebola outbreak in Sierra Leone was declared over on 7 November, but in neighbouring Guinea, people are still being infected by a disease which has claimed more than 11,000 lives in West Africa. But despite the unprecedented scale of the epidemic, there is still much that we do not know about Ebola. How long does the virus survive? Could Ebola become endemic in the region? What medical challenges do survivors face? MSF public health specialist Dr Armand Sprecher provides some answers.

Why is Ebola still a danger in West Africa?

The Ebola outbreak has been declared over in Sierra Leone, but there are still new cases in Guinea. Three new patients (including a pregnant woman) were admitted to MSF’s Ebola management centre in the capital, Conakry, two weeks ago, and a baby was born with the disease – and is still alive. Two of our patients belong to a known chain of transmission linked to a community death in Forecariah, but one comes from a transmission chain unknown so far.

Today, the main risk is the weak monitoring system. There are an estimated 233 people in Guinea who have come into contact with an Ebola patient but who are not being followed. It might be that a patient took a shared taxi, but the health authorities have been unable to find the taxi driver or the other passengers in the car.

This is why it is so difficult to stop the epidemic. The outbreak may be over in Sierra Leone, but as long as Ebola is still present in Guinea, the disease will stay on its neighbour’s doorstep and there will be a risk of new cases. Vigilance and the capacity to respond quickly to potential new cases will have to be maintained in the region.

Could Ebola become endemic in West Africa?

There are two possible routes to a disease like Ebola becoming endemic. First, there could be a lot of ‘late cases’, with people infected through sexual transmission – but we haven’t seen that happen. Most of the male survivors of a sexually active age had the disease a year ago. So if sexual transmission happened to a significant extent, we would have seen many more cases.

Secondly, the virus would have to adapt well to its new host. Viruses that have successfully emerged from their animal reservoir to become endemic in humans – such as HIV and measles – have often come from animals that are evolutionarily close to us. The Ebola virus, however, started with bats and is not well suited to human beings, and compared to other pathogens, it does not mutate quickly.

Also, the way the Ebola virus causes disease in humans is not conducive to it becoming endemic. Unlike other viruses, it doesn’t spread easily to casual contacts – for example, it isn’t transmitted to people passing in the street, like influenza. Instead it spreads through unsafe burials and caring for sick patients. When the risks are understood, and when the end of the chain of social networks is identified, the disease can be stopped in its tracks. That’s how the Ebola epidemic has been brought to a halt in other 

Can the virus survive after a patient has been cured?

Among the 27,000 cases of Ebola registered so far, we have observed a few ‘late cases’ in which the virus has embedded itself in sites in the body where the immune system is less present, for example in the testes, brain and inside the eyes. Most of these sites are not locations where the virus can easily spread outside the survivor to infect others, semen from the testes being the one exception. But these events are rare, and there are not enough of them to generate many new cases.

These cases show that there is a potential residual risk from survivors, but at the moment it is not quantifiable. In any case, focusing on the risk posed by survivors could be very misleading and take attention and resources away from more generalised surveillance. It is crucial to maintain a surveillance system which is not solely focused on the potential transmission from survivors. Science should now be at the service of Ebola survivors and not the other way around.

What are the medical challenges for Ebola survivors?

There are an estimated 15,000 Ebola survivors in West Africa, many of whom have ongoing physical and mental health problems. The physical problems include joint pain, chronic fatigue, hearing difficulties and eye problems, which could lead to blindness without prompt access to specialised care. The experience of being infected with Ebola and spending time in an Ebola management centre, as well as all the fear surrounding the virus, can lead to severe depression, post-traumatic stress disorder and mental health problems, including persistent nightmares and flashbacks.

But despite their needs, Ebola survivors can have difficulties accessing health services. Today, there is still some fear among health workers about treating Ebola survivors, while accessing health services can be economically challenging for people who have lost their jobs. It is essential that health authorities and all those involved coordinate their efforts to guarantee timely access to free quality care for survivors and their families.