I guess we shouldn’t post blogs on a Monday. We thought we had summed up the Ebola situation quite nicely on the 22nd only to find out that the authorities had plenty of surprises up their collective sleeves. It all started with a Tuesday mid-morning release from the CDC. Those worthies said that world efforts to control Ebola in West Africa might be working, more or less, but if they didn’t we could see 1.4 million cases by the end of January.[1] Wow! That’s worse than anything we ever came up with, and we’re not cheerful optimists.

So how did CDC do it? Well, we sat down with our trusty Cheat Sheet, modified it[2] to show CDC’s results, and decided we could reach the same result if (a) actual cases at the end of September are 21,000, and (b) they double thereafter every 20 days.

  • The first point is not surprising. CDC’s general view is that official figures grossly undercount actual Ebola cases in West Africa. This time around CDC put a number on it. They multiply the official count by 2.5 to get what is, in their view, a more accurate figure.
  • In the past we’ve used 35 days [i.e., 5 weeks] as the time required for Ebola cases to double. We don’t have any special knowledge in this area, but instead relied on an August 28 science report from WHO.[3] If CDC has new data, showing a much shorter cycle [i.e., less than 3 weeks], who are we to quarrel with them or their findings?

These adjustments are even more startling if we extend the trend out beyond 1.4 million cases. Doing that we find the entire planet could be or will have been sick with Ebola by October of 2015. Of course, that assumes Ebola won’t be contained in West Africa, and all the responsible authorities say it will. So I guess we shouldn’t worry.

What did the man say? Oh yes, “assure me no assurances.”[4] Perhaps the epidemic will burn out in West Africa, or perhaps it will spread far beyond that. Plagues do tend to spread. The only thing we know for sure is that, in time, we’ll find out.

Let’s move on to the recent science report from the WHO Response Team on Ebola, also published yesterday.[5] It’s full of lots of interesting observations. Take, for instance, the survival rate of people who catch Ebola. Lately there’s been happy talk in the media to the effect that this Ebola outbreak is not nearly as deadly as earlier ones. Why, it may be that up to 50% survive. Not so, say the WHO scientists. Actually the death rate is near 70%.[6] “The majority of patients are 15 to 44 years of age [49.9% male] and we estimate that the case fatality rate is 70.8% …”[7]

So why does the current outbreak seem to be spreading like gangbusters? With that many fatalities it seems there would be less people to spread it, and the ones who recover should be immune. Over time the population susceptible to the disease should decrease to the point that the virus can no longer sustain itself. Well, that might be true in a rural environment, where people are isolated and don’t travel much. However, that’s no longer true in West Africa. “The population of Guinea, Liberia and Sierra Leone are highly interconnected, with much cross-border traffic at the epicenter [of the outbreak] and relatively easy connections by road between rural towns and villages and between densely populated national capitals.”[8]

So modern transportation is a key to spreading Ebola? Gee, we have transportation in this country as well, and so does much of the rest of the world. Does that mean we’re all in trouble?

That’s a rhetorical question; let’s move on. How does one lessen the spread of an infectious disease? Well, by taking its sick [and contagious] victims out of circulation. The WHO report indicates that, once symptoms appear in a victim, it can take from 5 to a maximum of about 40 days to hospitalize that person. That “clearly needs to be reduced.”[9] To do that, of course, one needs to have the hospitals or treatment centers available to receive patients.  Also, it would be nice to have a vaccine, but it’s unlikely such things will be available for many months, if at all. Future possibilities cannot affect current efforts to control the disease.[10]

Given this gloomy picture, the WHO Response Team seems to be more or less in sympathy with the more alarmist predictions of the CDC. “Forward projections suggest that unless control measures … improve quickly, these three countries [Liberia, Guinea and Sierra Leone] will soon be reporting thousands of cases and deaths each week, projections that are similar to those of the Center for Disease Control and Prevention.”[11]

So there you have it. Now let’s wait for tomorrow.


[1] See The Washington Post, Sun et al., CDC: Ebola could infect 1.4 million in Liberia and Sierra Leone by end of January (September 23, 2014), available at:   http://www.washingtonpost.com/national/health-science/cdc-ebola-could-infect-14-million-in-west-africa-by-end-of-january-if-trends-continue/2014/09/23/fc260920-4317-11e4-9a15-137aa0153527_story.html

[2] The new version is called Cheat Sheet 3, and is available on request.

[3] See Sciencexpress Reports, Gire et al., Genomic surveillance elucidates Ebola virus origin and transmission during the 2014 outbreak (28 August 2014) (hereafter cited as Genomic Surveillance at __), available at http://www.sciencemag.org/content/early/2014/08/27/science.1259657.full.pdf

[4] Actually, I prefer this from Rod Serling: “It may be said with a degree of assurance that not everything that meets the eye is as it appears.” See http://www.quotes-encouraging.com/quotes/assurance/

[5] See New England Journal of Medicine, WHO Ebola Response Team, Ebola Virus Disease in West Africa, The First 9 Months of the Epidemic and Forward Projections (September 23, 2014) [hereafter cited as Sept. WHO Response Team at __], available at  http://www.nejm.org/doi/full/10.1056/NEJMoa1411100?query=featured_home

[6] See BBC News [Health], Briggs, Ebola death rates 70% – WHO study (23 September 2014), available at http://www.bbc.com/news/world-africa-29327741

[7] See Sept. WHO Response Team at p. 1 of 10.

[8] See Sept. WHO Response Team at p. 5 & 6 of 10.

[9] See Sept. WHO Response Team at p. 6 of 10.

[10] See Sept. WHO Response Team at p. 7 of 10: “Experimental therapeutics and vaccines offer promise for the future but are unlikely to be available in the quantities needed to make a substantial difference in control efforts for many months, even if they are proved to be safe and effective.”

[11] See Sept. WHO Response Team at p. 7 of 10.