There are still great challenges and great dangers — more on that later — but the big news is the abatement of the epidemic in Liberia.
Miracle in Liberia
Here is WHO’s chart of new cases in the country as a whole, and in the Montserrado district (which includes the capital, Monrovia). [WHO Current Ebola Situation Report]
The drop, starting in mid-September, is breathtaking, even when figures from the patient database are adjusted by more realistic situation reports. There is now a big oversupply of isolation beds in Monrovia, and in some other parts of the country. The ready availability of beds certainly contributed to the drop in new cases, but other factors must also be at work since the fall began while all available beds were still occupied. I speculated on the reasons for the apparent drop in my previous post: Too Good to be True? I don’t have much to add, except that behavior must have dramatically changed in Liberia. Changing people’s behavior is very hard, especially when it relates to deeply-rooted cultural norms such as caring for loved ones and religiously-mandated burial practices. The message from Liberia is that behavior change is possible, and it can stop Ebola (in its current form) in its tracks.
The magnitude of the change is dramatic. The Reproduction Rate (defined in The Ebola Chain Reaction) for Liberia had been estimated in September at 1.51 [NEJM 9/23/14] , which is consistent with the left half of the charts shown above — exponential growth. The right half of these curves implies a Reproduction Rate far below the steady state of 1.0, which means that the rate dropped by at least a factor of two in a period of just a few weeks. It’s marvelous that such a large change was possible in such a short time frame. This affords a solid basis to hope that the same can be accomplished in the other affected countries.
The epidemic is by no means over in Liberia! We must not let down our guard, or infection rates could jump up again. But we can certainly take heart. It might also be reasonable to mothball the construction of new isolation facilities in Monrovia, keeping open the option of finishing them if they are ever needed. To the extent possible, new facilities should be constructed in Sierra Leone and Guinea, or perhaps under-served parts of Liberia, rather than in Monrovia.
Steady Rate in Guinea
The rate of new cases jumped dramatically around the end of August and has continued at more or less the same level. This is a continuing severe epidemic, with Reproduction Rate around 1, but it is growing slowly if at all.
WHO’s helpful situation report breaks the results down by region and points out a particular vulnerability in the northern area adjacent to Mali, which may lead to further spread to that country. [WHO Current Ebola Situation Report] This is still a desperate crisis, but the slow rate of growth gives us time to get ahead of the situation. And the example of Liberia shows that control is possible.
Exponential Growth in Sierra Leone
The big worry now is Sierra Leone, where the rate of new cases is continuing to grow exponentially.
Growth in Sierra Leone is country-wide, but the capital of Freetown presents the most acute problem because it is running out of beds. Once again, the WHO situation report describes what’s happening and the management plan: [WHO Current Ebola Situation Report] We just have to hope that the miracle in Liberia can be replicated in Sierra Leone.
Concluding Observations
Just a few weeks back Liberia was the greatest worry, and the focus was on building isolation facilities there, especially in Monrovia. Now many of those facilities stand empty. Like a wily prize fighter Ebola ducked the roundhouse punch we had planned for it there, and is continuing to fight in other parts of the ring. This doesn’t mean that our plans were mistaken, or even unnecessary, since nobody could have foreseen the dramatic drop in transmission in Liberia. But it does mean that we need to be nimble in responding to where the greatest need currently is — Sierra Leone and the northern districts of Guinea. The need to redeploy resources is problematic, since it takes time and effort to design, build and staff a new facility. We have no choice, however: we must follow the epidemic wherever it goes.
So long as there is active transmission we are still exposed to two big risk factors:
- spread to another country with crowded slums, traditional practices and a weak healthcare system, and
- mutation to become more contagious.
I’m optimistic at this point that we can control the epidemic before either of these disasters occurs, but the need to end Ebola is still urgent.
Ebola Strategy 