Airborne Transmission of Ebola

An article which may point to weaknesses in the presumed safety practices in this New Ebola outbreak.

http://newsoffice.mit.edu/2014/coughs-and-sneezes-float-farther-you-think

Includes high speed video to show effects and longer distance than previously thought possible, thus calling into question the current “safe droplet separation distance” with regard to the spread of pathogens.

With New Ebola presenting flu like symptoms, including coughing and sneezing, it now appears as if virally loaded droplets may pass beyond the rule of thumb 3 foot contact zone for greater projection leaving traces on surrounding surfaces. And those distances are remarkably longer than suspected. In very dense populations such as the West Point quarantined zone, the narrow passages insure constant bumping and brushing against against sweaty neighbors and confining surfaces.

Skins swabs of non PPE wearing HCWs might be in order to test for the presence of EV.

The MIT study might also apply to the hand spraying of bleach solutions. Turbulence from the spray may lift deposited droplets into the ambient air before bleach solution makes contact. Total immersion into the bleach solution might make better sense.

As with any battlefield medicine, field expediant techniques may outpace laboratory testing without full understanding of why they work.

(Excerpt)

he paper, “Violent expiratory events: on coughing and sneezing,” was published in the Journal of Fluid Mechanics. It is co-written by Bourouiba, Bush, and Eline Dehandschoewercker, a graduate student at ESPCI ParisTech, a French technical university, who previously was a visiting summer student at MIT, supported by the MIT-France program.

Smaller drops, longer distances
The researchers used high-speed imaging of coughs and sneezes, as well as laboratory simulations and mathematical modeling, to produce a new analysis of coughs and sneezes from a fluid-mechanics perspective. Their conclusions upend some prior thinking on the subject. For instance: Researchers had previously assumed that larger mucus droplets fly farther than smaller ones, because they have more momentum, classically defined as mass times velocity.
That would be true if the trajectory of each droplet were unconnected to those around it.

But close observations show this is not the case; the interactions of the droplets with the gas cloud make all the difference in their trajectories. Indeed, the cough or sneeze resembles, say, a puff emerging from a smokestack.

“If you ignored the presence of the gas cloud, your first guess would be that larger drops go farther than the smaller ones, and travel at most a couple of meters,” Bush says. “But by elucidating the dynamics of the gas cloud, we have shown that there’s a circulation within the cloud — the smaller drops can be swept around and resuspended by the eddies within a cloud, and so settle more slowly.

Basically, small drops can be carried a great distance by this gas cloud while the larger drops fall out. So you have a reversal in the dependence of range on size.”

Specifically, the study finds that droplets 100 micrometers — or millionths of a meter — in diameter travel five times farther than previously estimated, while droplets 10 micrometers in diameter travel 200 times farther.

Droplets less than 50 micrometers in size can frequently remain airborne long enough to reach ceiling ventilation units.

A cough or sneeze is a “multiphase turbulent buoyant cloud,” as the researchers term it in the paper, because the cloud mixes with surrounding air before its payload of liquid droplets falls out, evaporates into solid residues, or both.

“The cloud entrains ambient air into it and continues to grow and mix,” Bourouiba says. “But as the cloud grows, it slows down, and so is less able to suspend the droplets within it. You thus cannot model this as isolated droplets moving ballistically.”

(Cut)

Lidia Morawska, a professor at Queensland University of Technology in Brisbane, Australia, who has read the study, calls it “potentially a very important paper” that suggests people “might have to rethink how we define the airborne respiratory aerosol size range.”

However, Morawska also notes that she would still like to see follow-up studies on the topic.

The MIT researchers are now developing additional tools and studies to extend our knowledge of the subject. For instance, given air conditions in any setting, researchers can better estimate the reach of a given expelled pathogen.

“An important feature to characterize is the pathogen footprint,” Bush says. “Where does the pathogen actually go?

The answer has changed dramatically as a result of our revised physical picture.”
Bourouiba’s continuing research focuses on the fluid dynamics of fragmentation, or fluid breakup, which governs the formation of the pathogen-bearing droplets responsible for indoor transmission of respiratory and other infectious diseases. Her aim is to better understand the mechanisms underlying the epidemic patterns that occur in populations.

“We’re trying to rationalize the droplet size distribution resulting from the fluid breakup in the respiratory tract and exit of the mouth,” she says. “That requires zooming in close to see precisely how these droplets are formed and ejected.”

_______________________________

Question for the thread.

Has anyone come across a full Level-4 autopsy report and lab results from such? Hard to imagine that previously occurring in Africa. New Ebola is proving we know far less about the Ebola strains than we think.

“With New Ebola presenting flu like symptoms, including coughing and sneezing”

Frankly speaking, I have not come across any mention of a “New Ebola” or references to sneezing.

While I have seen indications in the early onset of Ebola Zaire where a minority of patients complained of a sore throat, I would think that coughing would be incidental at best due to nasal secretions..but Ebola in human form is not known to infect the lungs.

There is no current safe distance that I am aware of as it applies to distance from patients while in line of sight.. Ebola in all it’s forms can be transmitted via aerosols. The distance they travel would be a factor of droplet size and the force that ejects them. They can also land on surfaces and be picked up there.

Anyone entering a room with end stage or mid stage Ebola patients would be remiss not to use a mask, gown, eye protection and also to have the patient masked. prior to that, and until the virus load overwhelms the host, they don’t general shed through aerosols to my knowledge. But one would take precautions in any case.

The same sort of precautions should be used with hospitalized cases on influenza or any virus that can be transmitted in that way.

Cold Heat:" While I have seen indications in the early onset of Ebola Zaire where a minority of patients complained of a sore throat,
I would think that coughing would be incidental at best due to nasal secretions
..but Ebola in human form is not known to infect the lungs."

Autopsies are gruesome things to all but the already initiated and expierienced.
The last I knew , healthcare professionals were already overwhelmed trying to save the ill patient; most energy was being expended in that effort.
Even so ,there is difficulty in finding additional staff , much less replacements for the medical staff that are ill themselves.

I dont know the results of autopsies on the deceased who died from Ebola virus, or whether it specificly attacks the lungs, but this West African Ebola is acting differently than other strains of Ebola, especially from Equatorial Congo where Ebola was first found ever to exist.
It has previously been demonstrated in Weston Va. that Ebola has attacked lungs in siminans in lab test:
< ncbi.nlm.nih.gov/pmc/articles/PMC3210905/ >

Also there are certain stages of decompositon of an infected body where all organs are attacked by hemmoragic fever/Ebola .
The actual decomposition is seperated into five different stages: Fresh, Bloat, Active decay, Advanced decay,and Dry remains.
At Fresh: Autolysis, or Self-digestion, is the destruction of a cell due to the actions of its own bodily enzymes.
At Bloat: Bloat or putrefaction- this stage of death is marked by the production of vapors.
The body’s cells are rupturing and breaking apart, the tissue is being broken down by bacteria.
The intestines push out and are subjected to distension ; the implication is that bloat is caused by bacterial breakdown and bodily fluids are under pressure.
Thus deceased bodies and ill patients could spread the viri by the micro-vapors, or bodily fluids under pressure.
It should be noted that Dr. Brantly recently stated that he had followed all known medical protocals in treating his patients, and he still came down with Ebola.
Why else did CDC and WHO recently upgrade and reccomend N100 face masks, and full face shields instead of N95 masks which were the previous protocol ?
I think we are dealing with a 'new critter' here , perhaps a mutant varient which demands world medical attention,
and not simply quarentine, and let it run its course, in situ .

IIRC there are only 5 known versions of Ebola.

The last one added to the list was Reston, which is harmless to humans and resolves via our own immune system in all known human infected, and it’s harmless to Pigs, but a pig can harbor it and shed it through mucous.

Given the fact that this strain has been looked at and is said to be Ebola Zaire,(the worst of them) I have no reason to doubt those who have identified it. In addition to that it seems to act like it in terms of it’s propensity to kill it’s hosts.

The only difference between this outbreak and previous ones of Zaire, is that it traveled to the city’s as opposed to being naturally isolated in smaller communities. (this due I think to the more frequent use of motorized transport)

In all previous cases medical personel were infected and died, and in all other cases, the death rates varied from 60-90 percent.

It is known as well that Ebola can undergo slight mutations, but generally it get’s bottlenecked to where it cannot change enough to become a separate strain. It is resistant to RNA recombination because of it’s structure.

Lastly, the virus is thought now to be more than 10,000 years old. I think that based on that knowledge, one can assume that it does not mutate easily and therefore probably has not, with the exception I listed above.

As to the lung business...Yes, the autopsies of the monkeys in Reston revealed infiltrates in the lungs of the monkeys autopsied but there are a few issues with the conclusion.. One is that it was the Reston strain, and the second is that the autopsy results and the conclusions drawn from it were not enough to say specifically that the Virus was actually attacking the lung tissue as it was simply found in the lungs. They did not do enough to show that lung tissue was being attacked by it so there is much debate about that. No further work has been done on the issue that I can find. Also it’s necessary to say that Reston is not dangerous to humans. It’s only found in the Philippines and not in Africa.

As to the other stuff, bloat, putrefaction, etc....I can’t say, nor can anyone say that any last stage Ebola patient is safe in any way..all protections have to be observed. Gasses released and even breath are considered and have to be so. The physical size of a particle required to infect someone is very small due to the gross number of live virus that can be in a particle like a aerosol spray. And you can imagine all sorts of scenarios were a expelled droplet as small as fog, can be moved around by other forces such as turbulences, or air flows. But that is what the masks and eye protection is for. You can do all that in your head but what science and medicine deal with are the probabilities.

In the US, our infection wards use filtered air supplies separate from the rest of the hospital. They use negative pressure to keep the air from entering corridors, they use lighting and chemicals to kill surface virus and even virus in the air, should it be there.

They don’t have any of this in West Africa. They are working out of shanties, cheaply constructed buildings and even tents. They are re-using gowns and scrubs, gloves and masks..after washing..

This outbreak will end when it burns it’s self out by infecting what population it can reach. It will stop when it reaches the last one that it is allowed to reach. Those that survive will be fairly well immunized for quite a while and would require a large exposure to re-infect.

As usual, viruses of this type kill the young and the old, and I note that pregnant women have a high mortality. All this is known and was compiled about Zaire Ebola years ago.

They know what they have, and they know how to deal with it, but the outbreak will not stop until such time as people quit making mistakes with it. I am hoping to see some better numbers to fit a flattening out of the curve here. But there is no doubt that this is a really bad one, perhaps as bad as it can get. Having said that I have no concerns about it getting entrenched here or anywhere in the west.

In the mean time, we have some interesting drug treatments to increase that survival rate....and maybe one day a inoculation.

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