Not too long ago we did a post on Ebola, or more particularly on the strain of Ebola that’s currently rampaging through West Africa. Ebola has been around since 1976 and, up until this year, the worst epidemic on record was the first one.[1] Now, however, all of that has changed. Today’s epidemic is more virulent than anything we’ve seen heretofore, and the situation shows no signs of improving in the immediate future.

Nevertheless, there is news, and it’s a mixed bag of the good and no-so-good. The bottom line seems to be (i) geneticists know a lot more than they did about the origin and makeup of the Ebola virus, and (ii) international health officials hope to have the current epidemic stopped, or at least tamed, in a few months. Of course, the international program will cost quite a bit of money – in the area of half a billion U.S. dollars – but that’s not really very much compared to what we pay for the average war, earthquake, hurricane, etc. these days. And, of course, if Ebola is defeated in Africa, then perhaps we won’t have to fight it here.

Let’s start with the science. On August 28 of this year an international team of scientists and clinicians published the results of their recent study of the Ebola genome.[2] Admittedly I’m no geneticist, or doctor, either, but I like to read these kinds of reports to see what the experts are up to. Occasionally I even understand some of the points they make but, and here’s fair warning, dear reader, I can be wrong from time to time. That’s why I probably never will make it in radio or on TV. Most talking heads are never wrong about anything.

But I digress. The report describes the current Ebola outbreak as the largest ever; it started in Guinea, West Africa in February; then spread to Liberia (in March), Sierra Leone (in May) and Nigeria (in June). The current outbreak has a “case fatality rate” of 78%; and the number of cases doubles every 34.8 days. Today Ebola can be found in major cities, such as Conakry (Guinea), Freetown (Sierra Leone), Monrovia (Liberia), and Lagos (Nigeria).[3] Also, there is evidence that Ebola is beginning to manifest in the Democratic Republic of Congo.[4]

What does it mean to say that cases will double every 34.8 days? Well, basically that it will happen about 10 times a year.[5] So, if we start with 2,240 known cases as of August 17[6] of this year, and follow the mathematical progression, we might well end up with over 2 million cases at the end of 12 months.[7] That, of course, assumes all of our efforts to halt the spread of the disease will fail, which apparently nobody thinks is likely. More about that later.

It’s generally believed that strains of the Ebola virus have circulated undetected in animals for years and cross from time to time over to humans. This can happen when humans eat an infected animal or otherwise come in contact with one.[8]  But, in the present outbreak that doesn’t seem to be the case. Instead, it looks as though the virus came to Sierra Leone when a group of women attended the funeral of a traditional healer who had treated victims of Ebola and died of the disease. Many infections in the current outbreak may have stemmed from that single incident. [9] There’s no evidence subsequent human/animal contacts played a role in spreading the infection.[10]

Ebola today is virulent and by all appearances highly contagious. It also seems to mutate rapidly. The August report catalogs some 395 mutations in the virus and states that, while it can’t say whether these differences are “related to the severity of the [current Ebola] outbreak,” the data it offers should “provide a starting point for such studies.”[11] Hopefully scientists and their governments agree with that. It certainly would be nice to know how and why this particular version of the disease operates and spreads as it does.

Speaking of virulence, the August report was very much a joint effort; it was the work product of 58 people around the world who collected analyzed and interpreted data about the current epidemic. Unfortunately five of them – all of whom lived in Africa – didn’t live to see their report published. They perished instead of the disease they were studying.[12] In clinical terms they died of a nosocomial transmission, i.e., of a disease spread “within a health-care setting, such as a clinic or hospital.[13]  The popular view seems to be that health care workers who get sick in the hospital, at least in the Ebola context, probably do so because of their own carelessness. Either they fail to wear protective clothing or improperly sterilize needles or syringes.[14]

It would be insulting and quite likely wrong to apply this kind of analysis to the 5 authors who died. By all accounts they were professionals, and well acquainted with current techniques for controlling infection. The fact that they died anyway argues that there is some, as yet unappreciated, additional way the disease is transmitted.

We made this point in the last blog, arguing that the medical community should revisit the question of whether Ebola, or at least the current version of it, is transmitted through the air as well as by personal contact.[15] It doesn’t seem this would be a hard thing to test. The Government, ours or somebody else’s, could just go to Home Depot, buy a couple of thousand air cleaners with HEPA filters, put them in major clinics where Ebola victims are collected, run the cleaners for a month, then check the filters to see whether they’ve collected any Ebola. If Ebola is found, it probably came from the air.

Now let’s talk about the World Health Organization’s initiative.[16] On August 28 WHO published its “Roadmap” or plan for fighting the current Ebola outbreak. It focuses principally on West Africa, where the disease currently rampages, and proposes a complex set of measures to supplement and integrate local efforts to combat the disease. More importantly from a bureaucratic standpoint, it also proposes a budget for the total effort.

Proposed budgets contain assumptions and this one is no different in that regard. Table 4 to WHO’s budget[17] estimates that the program will manage some 20,000 Ebola cases over a six month period. While this is a large number, it’s far less than one might expect if cases double every 34.8 days. So in that regard WHO is quite optimistic. It’s assuming that early and vigorous efforts to contain the epidemic will succeed, even though currently there is no vaccine or cure for Ebola in the world’s medical tool bag. We should all hope that WHO is correct.[18]

Anyway, for those of us who track such things, we now have a metric. If Ebola cases continue to double every 34.8 days, that’s bad. If, instead, they follow the track laid down by WHO and top out at 20,000, that’s very good. The epidemic is under control.

Good luck to all of us!

 

[1] See HHS, CDC, National Center for Emerging Zoonotic Infectious Diseases, Ebola Hemorrhagic Fever Information Packet (2009). The document is available as a pdf download from HHS. You can find it at http://www.cdc.gov/vhf/ebola/pdf/fact-sheet.pdf . (Henceforth we’ll cite it as 2009 Information Packet at __.) There are, of course, later versions of this paper, but most of them are heavily edited and incomplete.

[2] 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

[3] See Genomic Surveillance at p. 1 of 10.

[4] See Healthmap.org, The Disease Daily, Skotnes, et al., Ebola Update: DR Congo Confirms New Outbreak (August 26, 2014) at http://www.healthmap.org/site/diseasedaily/article/ebola-update-dr-congo-confirms-new-outbreak-82614

[5] Actually, my calculator says 10.488 times a year. That’s 365/34.8.

[6] See Genomic Surveillance at p. 1 of 10

[7] Actually, with 2.294 million cases. Try doubling that 10 times for the next year, and you get really big numbers, i.e., well over 2 billion cases. Do it two more times and you will exceed the current population of the world. (According to Wikipedia, that’s over 7 billion people. Go to the Wikipedia website and search World Population or simply click here: http://en.wikipedia.org/wiki/World_population )

[8] See AAAS, Phelan, Science: Ebola Genomes Provide New Information on West African Outbreak (28 August 2014) at http://www.aaas.org/news/science-ebola-genomes-provide-new-information-west-african-outbreak “It is possible the one animal infected multiple people at the same time….Animal meat is often cut into pieces and sold at local markets … so an infected animal could have been distributed to multiple individuals. It is also just as possible that one person happened upon a dead animal infected with Ebola … and then passed it to other individuals…”

[9] See Genomic Surveillance at p. 1 of 10. “On May 25 … scientists confirmed the first case of EVD in Sierra Leone. Investigation … uncovered an epidemiological link between this case and the burial of a traditional healer …”

[10] See Genomic Surveillance at p. 1 of 10. “This West African variant likely diverged from Middle African lineages … crossed from Guinea to Sierra Leone in May 2014, and has sustained human-to-human transmission subsequently, with no evidence of additional [animal] sources.”

[11] See Genomic Surveillance at p. 2 of 10

[12]See Slate.com, http://www.slate.com/blogs/the_slatest/2014/08/28/ebola_paper_authors_died_five_victims_contributed_to_research.html?wpsrc=slatest_newsletter

[13] See 2009 Information Packet at p. 1 of 12.

[14] See 2009 Information Packet at p. 1 of 12: “In African health-care facilities, patients are often cared for without the use of a mask, gown, or gloves. Exposure to the virus has occurred when health care workers treated individuals with Ebola HF without wearing these types of protective clothing. In addition, when needles or syringes are used, they may not be of the disposable type, or may not have been sterilized, but only rinsed before reinsertion into multi-use vials of medicine. If needles or syringes become contaminated with virus and are then reused, numerous people can become infected.”

[15] How could this happen? Take a look at 2009 Information Packet at p. 8 & 9 of 12: “Small particles of many different sizes contaminated with the infective agent may rise up from soil, clothes, bedding or floors when these are moved, cleaned or blown by wind. These dust particles may be fungal spores—infective agents themselves—tiny bits of infected feces, or tiny particles of dirt or soil that have been contaminated with the agent.” There are lots of other mechanisms as well.

[16] See World Health Organization, Ebola Response Roadmap (28 August 2014) (hereafter cited as WHO Roadmap at __), available at  http://apps.who.int/iris/bitstream/10665/131596/1/EbolaResponseRoadmap.pdf?ua=1

[17] See WHO Roadmap at p. 23, Table 4.

[18] But see WHO Roadmap at p. 24, Table 5. Table 5 forecasts that while 20,000 Ebola cases may arise, only about 1500 beds will be required for all Ebola Treatment /Centers. Is this because few who catch it survive the disease?

Advertisements