In a recent New York Times OpEd entitled What We’re Afraid to Say About Ebola, Michael Osterholm wonders whether Ebola virus could go airborne:
You can now get Ebola only through direct contact with bodily fluids. If certain mutations occurred, it would mean that just breathing would put one at risk of contracting Ebola. Infections could spread quickly to every part of the globe, as the H1N1 influenza virus did in 2009, after its birth in Mexico.
Is there any truth to what Osterholm is saying?
Let’s start with his discussion of Ebola virus mutation:
But viruses like Ebola are notoriously sloppy in replicating, meaning the virus entering one person may be genetically different from the virus entering the next. The current Ebola virus’s hyper-evolution is unprecedented; there has been more human-to-human transmission in the past four months than most likely occurred in the last 500 to 1,000 years.
When viruses enter a cell, they make copies of their genetic information to assemble new virus particles. Viruses such as Ebola virus, which have genetic information in the form of RNA (not DNA as in other organisms), are notoriously bad at copying their genome. The viral enzyme that copies the RNA makes many errors, perhaps as many as one or two each time the viral genome is reproduced. There is no question that RNA viruses are the masters of mutation. This fact is in part why we need a new influenza virus vaccine every few years.
The more hosts infected by a virus, the more mutations will arise. Not all of these mutations will find their way into infectious virus particles because they cause lethal defects. But Osterholm’s statement that the evolution of Ebola virus is ‘unprecedented’ is simply not correct. It is only what we know. The virus was only discovered to infect humans in 1976, but it surely infected humans long before that. Furthermore, the virus has been replicating, probably for millions of years, in an animal reservoir, possibly bats. There has been ample opportunity for the virus to undergo mutation.
More problematic is Osterholm’s assumption that mutation of Ebola virus will give rise to viruses that can transmit via the airborne route:
If certain mutations occurred, it would mean that just breathing would put one at risk of contracting Ebola. Infections could spread quickly to every part of the globe, as the H1N1 influenza virus did in 2009, after its birth in Mexico.
The key phrase here is ‘certain mutations’. We simply don’t know how many mutations, in which viral genes, would be necessary to enable airborne transmission of Ebola virus, or if such mutations would even be compatible with the ability of the virus to propagate. What allows a virus to be transmitted through the air has until recently been unknown. We can’t simply compare viruses that do transmit via aerosols (e.g. influenza virus) with viruses that do not (e.g. HIV-1) because they are too different to allow meaningful conclusions.
One approach to this conundrum would be to take a virus that does not transmit among mammals by aerosols – such as avian influenza H5N1 virus – and endow it with that property. This experiment was done by Fouchier and Kawaoka several years ago, and revealed that multiple amino acid changes are required to allow airborne transmission of H5N1 virus among ferrets. These experiments were met with a storm of protest from individuals – among them Michael Osterholm – who thought they were too dangerous. Do you want us to think about airborne transmission, and do experiments to understand it – or not?
The other important message from the Fouchier-Kawaoka ferret experiments is that the H5N1 virus that could transmit through the air had lost its ability to kill. The message is clear: gain of function (airborne transmission) is accompanied by loss of function (virulence).
When it comes to viruses, it is always difficult to predict what they can or cannot do. It is instructive, however, to see what viruses have done in the past, and use that information to guide our thinking. Therefore we can ask: has any human virus ever changed its mode of transmission?
The answer is no. We have been studying viruses for over 100 years, and we’ve never seen a human virus change the way it is transmitted.
HIV-1 has infected millions of humans since the early 1900s. It is still transmitted among humans by introduction of the virus into the body by sex, contaminated needles, or during childbirth.
Hepatitis C virus has infected millions of humans since its discovery in the 1980s. It is still transmitted among humans by introduction of the virus into the body by contaminated needles, blood, and during birth.
There is no reason to believe that Ebola virus is any different from any of the viruses that infect humans and have not changed the way that they are spread.
I am fully aware that we can never rule out what a virus might or might not do. But the likelihood that Ebola virus will go airborne is so remote that we should not use it to frighten people. We need to focus on stopping the epidemic, which in itself is a huge job.
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What about the other half? Is anybody listening?
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It’s in America now. What next. Is anybody listening? Got a cure?
Hi Vincent, love your blog. I think you make a fair point about the relative unlikelihood of a major switch of transmission type in Ebola. I think it is likely a relatively low probability event (but not vanishingly small). However, I do take issue with some parts of this post which I think overstate the case against such a switch occurring. Most importantly, I think you are understating just how different this current outbreak is, in terms of the potential for novel viral evolution, compared to previous outbreaks. I also think that our understanding of viral evolution in general and Ebola biology in particular is too limited to make confident predictions about exactly how likely a switch to airborne transmission is. Unlikely? Sure. Less than 1% chance? I have no idea.
“But Osterholm’s statement that the evolution of Ebola virus is ‘unprecedented’ is simply not correct. It is only what we know. The virus was only discovered to infect humans in 1976, but it surely infected humans long before that. Furthermore, the virus has been replicating, probably for millions of years, in an animal reservoir, possibly bats. There has been ample opportunity for the virus to undergo mutation.”
While it almost certainly infected *individuals* and occasionally small villages, I strongly suspect that there has never been anything even remotely close in scale to this current outbreak prior to the discovery of Ebola. There just wasn’t the population density or mobility necessary for such an outbreak -similarly to HIV/SIV, which possibly would never have been more than an odd occasional zoonotic agent if not for the encroachment of civilization.
As for Ebola’s evolution in its animal reservoir, that’s such an utterly different environment from humans that I don’t think it’s really relevant to questions of evolution in humans. The selective forces in the natural host of a virus are likely to be very different from those in a new host that it has not adapted to. I mean, heck, for all we know it could already be airborne in bats. I can’t imagine anyone has looked.
We know from paleovirology that sequence evolution of RNA viruses is actually highly constrained over deep time, suggesting strong purifying selection, probably due to the relentless but relatively unchanging selective pressures of their host species. However we also know that switching to a new host can often lead to an increase in positive selection of adaptive mutations, and indeed, from Gire *et al* it looks like the rate of sequence change is twice as high *within* this outbreak as it is between outbreaks. This is not business as usual, this is a new evolutionary landscape for the virus, and it is almost certainly adapting to this environment. In what ways? I don’t know, but increased transmissibility in some form or fashion would seem likely.
“The message is clear: gain of function (airborne transmission) is accompanied by loss of function (virulence).”
In flu. Specifically, this strain of flu, in ferrets. I honestly don’t see how this is relevant to Ebola. We don’t even understand how these mutations are improving transmission; how can we generalize to other viruses without any knowledge of the mechanism?
“The answer is no. We have been studying viruses for over 100 years, and we’ve never seen a human virus change the way it is transmitted.”
I would argue that Ebola virus is not really a human virus yet, evolutionarily speaking. It’s a zoonotic infection that happens to have a fairly decent rate of human to human tranmission, but it hasn’t really made the switch in terms of becoming adapted to human infection. Thus, human viruses (except maybe HIV, since it’s close to its zoonotic roots still) are not really the proper paradigm. We want to look at viruses infecting a new host -ideally a lot of them, so we can get an idea of the spectrum of possibility. How do they adapt? Are the pressures primarily from immune factors, or do they also have to, say, alter their transmission profile, or cell tropism? Then maybe we can look at Ebola in humans and see if it has features analogous to one or more other zoonotic infections.
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Can someone please discuss the Reston outbreak, and whether it was airborne?
I’m no expert, nor do I claim to be. But I find the simple premise that “viruses do not evolve their method of transmission” to be yet another example of “Think Tank Hubris” otherwise known as living in “The Star Chamber”.
Simplistic analysis such as this article premises is more of the same that we got from so-called experts concerning Fukishima. Current reality seen they were wrong, and I suspect that this article’s author’s will live to eat their own words.
Let’s not forget the Canadian equivalent of the CDC who stated and observed aerosol transmission of this (or an offshoot) virus among mammals. Also the number of smart health care workers who have been infected with this disease, in spite of protections that address known transmission protocols, tells me this article is nothing more than whistling past the grave yard.
I pray you are correct, I believe you are wrong. I hope you “win” his contest of opinion.
Just A Schmo…
H1N1 is now know to have infected marine mammals. Invertebrates virus? Very seldom is any human health problem mentioned when it comes to ballast water.
It’s in the USA now. IVC may be the only real hope, if you get Ebola. http://www.naturalhealth365.com/natural_cures/ebola-virus-t
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The really bad part about this is that the world needs an out break in order to keep the population in check. The world is grossly over populated
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How about Reston Ebola? Any discussion?
Yes, smart health care workers working in sub-standard, combat-like conditions and with such an urgency to help their fellows that they delivered babies,from Ebola-infected nurses, were working so feverishly they might well have contracted it while removing protective gear between patients, while some teams of doctors had to themselves clean wards. Given the slow international response to this outbreak, and that so much of it has been in urban environments where it is more difficult to contain, the nature of the countries where Ebola took route (Liberia! The other locales also destabilized by civil war), it is a wonder MORE health workers, even yes, well trained and skilled specialists, have NOT contracted it.
In Liberia, since the civil war, there is an impossibly low ratio of doctors to patients. The few doctors who could attend to early cases (was it 51 doctors in the whole country?) suffered rapid attrition, leaving a few few to serve a population of 70,000. Health workers deserted some hospitals in other countries. Without any staff, a heroic doctor will surely be at more risk as she battles on, mopping up, taking blood samples, decontaminating the ward, and performing surgery.
Given all the circumstances, so far the fact that health care professionals, including some in protective gear with a knowledge of how to use same, have died from the virus is a) nothing new b) does not prove the virus has become more virulent or changed its means of transmission.
No assurance the world won’t blow up tomorrow. As you say, the human handlers were not endangered. The proof is in the pudding.
So far, none of the known of the five Ebolas has been airborne in terms of transmission to humans.
That viral matter can be aerosolized (as all fluid can be) is not the same as that virus having become airborne!
I think it more helpful in the long-run to worry about what HAS happened, to use past history to make future predictions, as there is work to do, much, to contain the current outbreak and enough airborne viruses to wring our hands over.
Thank you!
This particular strain could be spread by aerosol means. Come on folks. And as far as stopping the epidemic. Stop bringing infected people back to the U.S. and importing the virus. Put them all in a centralized area at least. Stop spreading them and the virus all over the country. Mother Nature can’t be controlled. She’ll adapt and do as she always has. Ebola Reston spread through aerosol means. And let’s not forget the Canadian study. The U.S. has known for over 20 years that Ebola could be transmitted this way. For anyone to say for certain that this strain isn’t spread this way is irresponsible. These medical workers are trained and yet accidents can happen. They have protective gear yet they are still being infected. You can’t possible believe this is all occurring from contact with bodily fluids. The numbers for the transmission of the virus among medical personnel is enough for anyone to see it’s spreading through aerosol means.
Vitamin C deficiency is very rare in the tropics. It’s other forms of malnutrition that are common: protein energy malnutrition (PEM, kwashioror), beri-beri (thiamine deficiency), iron deficiency anaemia etc.
That is simply wrong.
While I agree that it’s unlikely to become airborne, have to take issue with the remark that: ‘The message is clear – “Gain of function” is accompanied by “loss of function”.’ That’s talking about something which was observed in an H1N1 experiment. It has F all to do with hypothetical “airborne Ebola”. Becoming airborne doesn’t guarantee to bring with itself some “loss of function”. There is no universal LAW OF THE CONSERVATION OF AMOUNTS OF DANGER. LOL. Apart from that, largely agree…
Most “airborne” diseases are really just “respiratory or nasal passage infections” which cause profound sneezing and coughing lol. So if you did that while you had Ebola, it would i am sure be airborne too. It just happens to not cause so much constant coughing and sneezing so not such large amounts of fluids are ejected into the air in that manner. That’s all it means really. It’s more a description of how the patient behaves while very sick rather than something inherently true about the virus itself. It could definitely make it across a few feet of air if a patient had a massive coughing fit and there was sputum flying…no doubt. It just doesn’t cause much coughing and sneezing.
Has anyone studied this particular strain to rule it out in this particular case? This particular strain has behaved differently to previous outbreaks in a few ways, such as getting established in three different countries at once. Normally it didn’t get as high even in one country, let alone in three at once. I’m sure you can’t put that ALL down to mismanagement.
The amount of “epidemiological evidence” available in the CURRENT outbreak exceeds the sum of all previous outbreaks since 1976, by more than a factor of 2 at the last count. It’s just not clear anyone has measured the properties you are describing for THIS outbreak.
Has anyone measured “droplets at close range” in Freetown and compared it to previous outbreaks?
There was a study [with the laboratory strain, though] proving “droplets at close range” is a possible vector between a pig cage and some monkeys in a cage on the other side of a wire fence to the pigs. So that was airborne. Close range mind you.
If it becomes properly airborne to the same extent as SARS then we would be completely screwed anyway to be fair, and just have to wait for half the population of the world to expire then attempt to rebuild it. You can worry about it. Or just get on.
It is a fact there is no particular reason to worry about it becoming as infectious through the air as SARS, anyway. Ebola is a huge concern AS IT IS. We don’t need to worry about EXTRA BAD versions of it that MIGHT come into existence lol (but very very unlikely). The current Ebola is already a massive challenge!
We probably don’t have that kind of research data. The hospital staff are too overworked with the basics due to the fact they do not have enough beds.
Less than half bled in some outbreaks. more than half had some bleeding. a minority had a lot of bleeding. severe bleeding – like the truly horrific pictures – is worst case, but relatively rare. Very many illnesses has a truly horrific worst case. Ebola is not a pleasant death though but that is a lot due to the kidney and liver failure and the fever, however on the plus side you do become delirious. 🙂
It was airborne but did not produce symptoms in humans, just antibodies. Not 100% sure though, anyone read the Hot Zone?
What I’ve discovered since asking my question is this:
—————–
Is it airborne?
Scientific definition? No. It does not float indefinitely on dry dust particles and VERY few viruses can.
Common definition? It always had been. Ebola spreads the same way influenza does. Via fluid droplets. When you cough or sneeze or puke, or pee, have projectile diarrhea, or otherwise propel body fluids in to the air ‘water’ droplets are misted in to the air and float around as a thin mist. Depending on air circulation it can take many hours for these droplets to settle and they do so after having drifted clear across the room contaminating both the air and then the surfaces they settle on. Touch a surface contaminated by these droplets, breathe in air with these droplets in it, or have the droplets in the air hit you in the mouth/nose/eye/etc and you can get ebola.
—————–
Source: http://www.survivalistboards.com/showpost.php?p=6986325&postcount=3475
That’s actually not what it’s all about. For example, individuals infected with influenza virus shed virus during the incubation period, even in the absence of coughing and sneezing. Whether a virus is airborne transmissible is certainly multifactorial. No one questions that Ebola virus is probably infectious in large droplets that can be expelled onto mucus membranes of nearby individuals. What it’s not able of doing is staying suspended in the air and being inhaled into the respiratory tract. Why exactly that is, is hard to say.
The Canadian laboratory observed possible airborne transmission between pigs and monkeys. Pigs manifest a respiratory illness following Ebola virus infection, which is very different from the disease observed in primates. In addition, the authors of that paper acknowledged that due to the design of the facility they couldn’t exclude the possibility that large droplets were expelled into the monkey cages, and that those droplets, rather than actual airborne transmission, was the mode of infection in monkeys.
Subsequent experiments in the same lab completely failed to demonstrate airborne transmission between monkeys.
It’s actually not even completely clear that the Reston outbreak was due to airborne transmission. That did seem the most likely explanation, but the facility practices were not so rigorous that other modes of transmission could be ruled out.
The point was merely that Ebola is not characterized by massive internal or external bleeding as it is sometimes depicted. Hiccups are actually much more strongly correlated with fatal outcome than bleeding, though bleeding certainly isn’t good. But people don’t die due to blood loss, though it’s not always clear what the actual cause is. Some speculate sudden cardiac arrest due to electrolyte imbalance, shock leading to multiorgan failure, etc.
Um, please explain why you have reasoned that a post from “Colt” on the survivalist boards is reliable enough to be repeated here? Thanks.
Isn’t the availability of fruit in Africa what allowed primates to survive without the ability to make their own vit. C? Interesting idea, but I highly doubt all these people are suffering from scurvy. Their toenails would be messed up.
His statement was a summary based on much discussion of the facts. I guess you had to be there.
Ebola is not a very serious virus..
Infact , I have a cure for it which I personally tested on me.
Not a Joke at all.
I also suffered from it. It mostly affected my right whole arm , left hand and left feet.
Their is no need to make a new medicine for it.
Just be cool , Really very cool.
Seriously , drinking chilled water all the time , Wearing summer clothes in winter , stay away from heat , bath with cold water even in winter , sit in front of an A.C most of the time and avoid Sunlight.
It feels like insects roaming on your back when you are not cool in any way.
In short , always Remain cool and try to make it a habit of yours.
This definately 1000% works as personally tested by me on me..
Contact me if need some info from me.
Thank You.
What word do you suggest as an experienced virologist?
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“…the H5N1 virus that could transmit through the air had lost its ability to kill. The message is clear: gain of function (airborne transmission) is accompanied by loss of function (virulence).”
For a virus, the “ability” to kill is not a useful function, it’s a detriment to virulence. A virus that kills its host quickly will have little time to spread on to a new host. Deadliness might be dramatic, but it’s not useful.
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Actually, there is. Think about it this way, very simple to understand: We evolved from fish… We gained our arms and legs (very helpful), but we lost our fins and tails. We gained function (walking on land, typing on computers), but we lost function (maneuvering through the ocean, swimming like a fish).
Very specific mutations must occur for the virus to MUTATE into airborne. These specific mutations affect the RNA in such a way that it can no longer “swim”. See?
It is kind of true for all of nature…
Law of conservation of energy and matter, etc.
Pretentious much?
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