Most of us know how to say nothing; few of us know when.

Anonymous[1]

[Let’s review the facts of Ebola one more time.  There are five strains of Ebola known to us.[2] The Ebola virus first appeared in 1976, and broke out 22 times from then to 2012, infecting a total of 2,315 individuals. The outbreak of 2013-2015, some call it an “explosion,” is far more infectious and deadly than all of the earlier ones combined.[3]  This time so far about 22,040 people have been infected[4] by it, or not quite10 times the total of all prior outbreaks.[5]

Seemingly the current outbreak is beginning to fade, but that’s not a foregone conclusion. At present there are no vaccines to prevent the disease, or cures to treat it. Our efforts to contain it have consisted almost solely of finding and isolating patients, and providing palliative care until they either recover or die. So even if the disease fades in one infected area or another, there is no guarantee that it won’t recur if infected people return to areas thought to be safe, or it spreads in some other manner. [6]

The Ebola strain that figures most prominently in the current outbreak is Ebola Zaire, and the good news is that we have a program to test the efficacy of a vaccine against it.[7] The bad news is that it may take up to a year for trials to be completed and, of course, the vaccine may fail. The other bad news is that Ebola viruses are thought to be mutating.[8]

We all remember the public consternation last summer when the current epidemic broke into prime time. The medical establishment rushed to assure us that America was not under a significant, direct threat. The virus, they said, spreads only if a person has direct contact with the bodies of people who died of it, or with bodily fluids of the sick. Also, people who are infected, but are not yet “symptomatic,” cannot spread the virus. You won’t catch it if you are sitting next to someone who is infected, but isn’t running a fever.

And finally, you can’t catch Ebola by breathing the same air as an infected person. There’s no truth to the rumor that the virus may spread “through the air.”

These assurances were quite, well, reassuring. They also made it easy to determine how anyone who was sick caught the disease. If someone had Ebola, he [or she] obviously had touched a dead body or the fluids of someone who had Ebola. If the sick denied that, they were either mistaken, or lying. This applied to everybody, even highly trained health care workers who were equipped with the latest protective devices. Regardless of training, if they got sick, obviously they had they had made an error protecting themselves; alternative explanations were not acceptable.

Not everybody believed this. Some amateurs, like us, thought that the reasoning in play seemed a bit circular. You know, like when a politician assumes a conclusion and disregards contrary evidence as being mistaken or possibly false. While politicians do that, we should expect more from scientists. Good scientists are supposed to be double-checking and revalidating their theories, not offering them as gospel truth.

And guess what? Last year some prominent scientists, a minority for sure, took the position that our clinical experience with prior Ebola outbreaks was too limited to justify blanket assurances about this one. [9] There might be a lot of gaps in “the science” as it now exists. [10] Dr. Michael Osterholm, of the University of Minnesota, was one of these. [11] He and a research team announced they would re-examine existing medical literature to determine what science really knows, and doesn’t know, about how Ebola spreads.[12]

And now the results are in. Last week the Washington Post reported that, in some cases, Ebola might just transmit through the air or in other novel ways.[13] The Post’s article was based on Dr. Osterholm’s study, which was published on February 19 by the American Society for Micro Biology.[14]

The Post’s article was interesting, but glossed over many details. So, we asked ourselves, do we have more to say about the subject? Of course we do.

You know how we operate here at Elemental Zoo Two. When a subject interests us we let the mainstream media trade on hearsay and rumors; extract stories from drunks in hotels, fashionable cocktail parties or other networks; use confidential sources; or rely on papers prepared by interns or junior staff. We, as reputable bloggers, look at the original sources, whether we understand them or not, and draw our own conclusions. That’s risky, of course; we have no one to blame but ourselves when we make mistakes. But so what?

So we retrieved Dr. Osterholm’s article and read it. For convenience we’ll call it the Osterholm Report, although he lists quite a few co-authors.[15] We fully understand that the report represents a team effort, and don’t want to imply otherwise. Also, it’s not an easy read. We spent several days reading and puzzling over it.

General Findings

The Report re-examined what we know, or think we know about how Ebola is transmitted and, more to the point, what factors might explain why the current epidemic dwarfs the combined total of all prior ones. Osterholm [and his co-authors] acknowledge that “direct patient contact and contact with infectious body fluids are the primary modes for Ebola virus transmission[16],” but argue that other factors may be present as well. They highlight six areas for further consideration.

  • Whether Ebola can be transmitted by aerosols generated in the vicinity of “source patients”;
  • The role of environmental contamination, especially in the health care setting;
  • The degree to which mildly ill patients can transmit an infection;
  • How long “clinically relevant” infectivity really persists;
  • Whether there are “super spreading events” that might magnify a transmission;
  • What role “sylvatic[17]” or domestic animals might play in propagating an outbreak once it has started?[18]

Aerosols

Aerosols were a big part of last year’s argument about Ebola transmission. The question was whether the virus could be transmitted in large droplets of fluid that directly hit the skin or mucous membranes of a victim, or by small particles of virus that are breathed in at a distance, or by both means. Seemingly if the general rule was that Ebola could not transmit through the air, then neither would be possible.

Recently both WHO[19] and CDC[20] produce studies that said it was unlikely the genetic makeup of one strain or another of the Ebola virus would change sufficiently to allow it to generate small particle aerosols. The Osterholm Report agrees with this in principle, i.e., that it’s unlikely such a thing would happen, but cautions that the current outbreak “surprised even the most astute infectious disease experts in the global public health community.” There’s always the possibility that Ebola could do it again.[21]

Moreover, there’s no reason to assume Ebola can spread by aerosol only if genetic changes are made to the virus. Phenotypic changes might accomplish the same thing. What’s a phenotypic change? That’s not clear from the article, but apparently it’s one that can’t be traced to changes in a genome.[22]

There are plenty of examples of aerosols being generated by coughing, vomiting diarrhea or medical procedures.[23] Also, generally “droplets involving respiratory pathogens are a heterogeneous mix of large and small particles.”[24] This wide range of particles might be easily inhaled by someone standing near the point of generation.”[25] Even if the small ones couldn’t infect someone, a large one might well do so.

That is, when aerosols are being generated, by vomiting, medical procedures, etc., the unlucky might catch Ebola simply by standing nearby and breathing in the large droplets; there would be no need to touch anything and, in any case, once a person is infected, it would be quite difficult to determine how it had happened.

So, if we’re drawing as conclusion from this, it’s that the Osterholm Report does not rule out the second possibility, at least in a clinical setting, where there’s a lot of vomiting or diarrhea, or medical procedures are being performed.

Environmental Contamination

So how long does the Ebola virus survive in an environment once it has presented itself? And where does it survive, in whom or in what? We have some data on these matters, but they are “very limited.”[26] The Report recommends further research in this area.

The Mildly Ill

The Report acknowledges that “in the vast majority of cases, infected persons do not transmit the virus in the absence of symptoms …” [27] Most likely this is because people who are infected don’t shed much virus until they run a fever or evidence other symptoms. While this is generally true, the Report recommends more research to refine our understanding of disease onset.

Length of “Infectivity”

People infected with Ebola can shed the virus for several months following their recovery. Does that mean that they can continue to spread Ebola for that period? The Report says that “the epidemiological significance of this remains unknown.[28] This should be researched as well.

Super Spreading Events

The current outbreak is characterized as “explosive.” It’s been hypothesized that virus spread is facilitated by behavioral factors, “such as “association with ritual burials;” if you bring a large group of people together, and they handle dead bodies, the virus might infect many at one time. That would be a “super spreading event.”

However, that one example does not exhaust the list of all possible such events. “[O]ther possible explanations deserve further investigation. It could be, as suggested by phylodynamic modeling, that [super spreading] events have played an important role in transmission dynamics in West Africa.”[29] What is “phylodynamic modeling?” For more information than you probably want, check out the Wikipedia entry on viral phylodynamics.[30]

Animal Infections

Various strains of Ebola have been detected in non-human primates, fruit bats, pigs, dogs and so forth[31]. It’s long been theorized that animals are the primary reservoir for the Ebola viruses when they’re not breaking out as epidemics among humans. Apparently there’s not much, if any, data on whether the virus crosses from animals to humans once an epidemic has started, or whether that’s a one-time event. In a large epidemic we don’t know “if [virus] transmission is amplified by sylvatic or domestic animal populations at the human-animal interface.”[32] Again, the Report suggests more research.

Conclusion

So there you have it: A convenient checklist of issues our scientists ought to look into before the next Ebola outbreak. This probably isn’t the only checklist that’s out there, but it’s the one we know about and, in our view, the Government should act on it. The necessary research needs to be commissioned, civilian or military, it doesn’t really matter; just find the people willing to do the work, and give them the resources they need.

Then, when the next outbreak occurs and all the Government and media people line up to tell us not to panic, they won’t sound like characters from a Stephen King novel.[33] You know, by telling us there’s no problem, everything will be fine, while the news from abroad shows something very different. Instead they’ll be able to say, “Your Government has been proactive; we’ve learned a lot since the last outbreak, and this time we can beat Ebola early and decisively.” That would be wonderful, if it’s true.

[1] We like this quote quite a bit. It’s too bad our politicians and media darlings don’t.  The quote is from Carruth & Ehrlich, The Giant Book of American Quotations (Gramercy Books 1988, 1999) at Conversation, p. 162, n. 1. Not as prestigious a source as the ODQ, but who are we to turn down a good quote?

[2] 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 __.) : “Four of the five have caused disease in humans: Ebola-Zaire, Ebola-Sudan, Ebola-Ivory Coast and Ebola-Bundibugyo. The fifth, Ebola-Reston, has caused disease in nonhuman primates, but not in humans.”

[3] See Scientific American, Fischetti, The Steady Rise of Ebola (February 2015) at p. 88. This is a nifty, one-page depiction of what happened between 1976 and 2012.

[4] This is from the WHO Situation Report of 28 January. It’s available from WHO, Ebola Situation Report (28 January 2015) at http://apps.who.int/ebola/en/ebola-situation-report/situation-reports/ebola-situation-report-28-january-2015  WHO also shows with 8,810 deaths. You can download the raw data from WHO, Ebola Data and Statistics, at http://apps.who.int/gho/data/node.ebola-sitrep.quick-downloads?lang=en

[5] That’s 22040/2315, or about 10.5 %.

[6] See BBC, News Africa, no author listed,  Ebola: Mapping the outbreak (23 January 2015), available at http://www.bbc.com/news/world-africa-28755033

[7] See BBC, News Africa, Doyle, First Ebola large-scale vaccine trial starts in Liberia (2 February 2015), available at http://www.bbc.com/news/world-africa-31100450

[8] See BBC, News Health, Mazumdar, Ebola outbreak: Virus mutating, scientists warn  (29 January 2015), available at  http://www.bbc.com/news/health-31019097

[9] See The New York Times, Osterholm, What We’re Afraid to Say about Ebola (September 12, 2014), available at http://www.nytimes.com/2014/09/12/opinion/what-were-afraid-to-say-about-ebola.html?_r=0

[10] See University of Minnesota, Center for Infectious Disease Research and Policy (CIDRAP), Roos,  Experts raise specter of more-contagious Ebola virus (September 12, 2014), available at http://www.cidrap.umn.edu/news-perspective/2014/09/experts-raise-specter-more-contagious-ebola-virus

[11] For the Wikipedia version of his biography, go to http://en.wikipedia.org/wiki/Michael_Osterholm

[12] See also Chicago Tribune, Editorial Board, What Ebola has taught us (December 26, 2014)  available at http://www.chicagotribune.com/news/opinion/editorials/ct-ebola-nih-cdc-who-sierra-leone-nigeria-osterholm-edit-1229-jm-20141226-story.html

[13] See The Washington Post, Bernstein, Limited airborne transmission of Ebola is ‘very likely,’ new analysis says (February 19, 2015), available at http://www.washingtonpost.com/news/to-your-health/wp/2015/02/19/limited-airborne-transmission-of-ebola-is-likely-new-study-says/ The study was officially announced at http://www.asm.org/index.php/journal-press-releases/93381-what-we-know-and-don-t-know-about-ebola-virus-transmission-in-humans

[14] For the abstract, go to the American Society for MicroBiology, Osterholm, et al.,  Transmission of Ebola Viruses: What We Know and What We Do Not Know (February 19, 2015), available at http://mbio.asm.org/content/6/2/e00137-15 . You can also download a full version of the study from this location. Henceforth we’ll cite the study as What We Know at __.

[15] The listed authors are: Michael T. Osterholm, Kristine A. Moore, Nicholas S. Kelley, Lisa M. Brosseau, Gary Wong, Frederick A. Murphy, Clarence J. Peters, James W. LeDuc, Phillip K. Russell, Michel Van Herp, Jimmy Kapetshi, Jean-Jacques T. Muyembe, Benoit Kebela Ilunga, James E. Strong, Allen Grolla, Anja Wolz, Brima Kargbo, David K. Kargbo, Pierre Formenty, David Avram Sanders, and Gary P. Kobingerc. Please accept our apologies if any of the names are misspelled.

[16] See What We Know at p. 1, Abstract.

[17] Strictly speaking, sylvatic animals live in the woods. Sylvatic diseases are diseases caught by wild animals. There’s a short entry on this in Wikipedia, at http://en.wikipedia.org/wiki/Sylvatic

[18] See What We Know at p. 1, Abstract.

[19] See What We Know at p. 9, n. 85.

[20] See What We Know at p. 9, n. 86.

[21] See What We Know at p. 6.

[22] See What We Know at p. 6. I think the authors are referring to a situation where people close by inhale an aerosol that contains large droplets. “[H]owever, with phenotypic changes in the virus, aerosol transmission (and possibly respiratory transmission if primary pulmonary infections were to occur) involving droplets of various sizes from cases in relatively close proximity to uninfected persons remains plausible.”

[23] See What We Know at p. 6.

[24] See What We Know at p. 5.

[25] See What We Know at p. 5.

[26] See What We Know at p. 6: “These findings are consistent with a review on particle size, which found

that droplets involving respiratory pathogens are a heterogeneous mix of large and small particles.

[27] See What We Know at p. 6.

[28] See What We Know at p. 6

[29] See What We Know at p. 6.

[30] It’s available at http://en.wikipedia.org/wiki/Viral_phylodynamics

[31] See What We Know at p. 3.

[32] See What We Know at p.6.

[33] The novel we have in mind is, of course, The Stand (Doubleday 1978, 1990), no doubt available from your local library; the first part graphically describes a plague that kills just about everybody while the Government, as long as it lasts, tells the public not to panic.

Advertisements