New WHO study on Ebola

So far, just under 6,000 people are estimated to have contracted the disease since the first cases were reported six months ago, just under three thousand have died. Dr Christopher Dye is the Head of Strategy at the World Health Organization (WHO) and a co-author of a new WHO study.

DW: Dr Dye, is Ebola now out of control in West Africa?

Christopher Dye: Ebola is certainly still increasing very quickly in West Africa. The message that we have delivered in the study that we just published [on 23.09.2014] is that if we don‘t take much stronger action to stem the increasing cases, we will be seeing not merely hundreds of cases and deaths per week but thousands. The study that we just published is therefore primarily a call to action. If that action is taken, we are confident that we can turn this epidemic around but if we don't do that, then as I say, we can expect the number of cases and deaths to go on rising.

So if 20,000 people are expected to have contracted the disease by the end of November, what is the figure going to be like for the new year?

We daren't predict that far. Others have taken that step, there has been talk of hundreds of thousands of cases, even millions of cases, but we can't possibly predict that far into the future. This epidemic is very much like weather forecasting, we can predict days or even two, three weeks into the future but not beyond that. So we have been more cautious in talking about what will happen up until the beginning of November. That's 20,000 cases or so, that's a tripling or thereabout of the case number we have seen at the moment. But what we are expecting quite honestly is that the control measures that are now being put in place both by external agencies (about which there has been much in the media recently) but also what the communities themselves are doing on the ground - we expect those combinations of things to have an impact on the epidemic and we expect to be able to see that quite soon.

Can you quantify that impact on the epidemic?

What we can quantify, because we have done it in the study that we just published, is that each Ebola patient is generating at the moment about two more cases, and the doubling time of the epidemic is about every three weeks. The consequences of our calculations are that if we can reduce person to person transmission by a factor of about two, then we can start making the case numbers go down. We can interrupt the chains of transmission and we can force the number of cases and deaths downwards on a week by week basis.

And what needs to be done then to stop this epidemic?

The basics of Ebola control are fairly simple. It's infection control and patient support. We would love to have vaccines and new drugs. We don't have them yet, they may be available some months down the line, but at the moment the control effort is based on stopping one person infecting another and we know how to do that because we have experience from previous epidemics. The key to it is as soon as people fall ill, they must report to a health center. If they can do that, and if they can be isolated, then we stand a good chance of stopping transmission from one person to another. But for any patient who has been identified, ideally we need to trace the contacts. It's very hard in a big city like Monrovia, the capital of Liberia, where we are seeing many cases. But in other areas it is possible to do that contact tracing. Also very important is safe burial. It's a tragedy of course when a family loses one of its members and local practices usually involves close contact with the deceased, touching body fluids and so on. If we can prevent that from happening, then we can stop major sources of infection in the community. So we know what to do. What we have to do is to ramp up the control efforts, and we are seeing that at the moment, and if we do that, then we expect to stop transmission.

What about the lockdown that was carried out in Sierra Leoneover the weekend? Is that a measure that the World Health Organization would support?

It‘s very difficult to predict what the outcome of a lockdown is going to be because there are forces that act in both directions. The logic of it from the perspective of government is to stop people moving around in the community which we know has been important in transmission. But on the other hand, where lockdowns take place, then of course people are confined to their houses. If they are infected, they are in close contact with other family members. And there is also the risk that cases will be missed. However, on the positive side, what was done in Sierra Leone recently is not just the lockdown - that was the headline news, but also house to house search which is potentially very positive in finding cases. And on top of that, it's a major statement of political commitment from the top of government and that will have had a major effect on people in the country.

Christopher Dye is Head of Strategy at the WHO and a co-author of a new WHO study on Ebola

Interview: Mark Caldwell