Corona Virus 2019-nCoV

Discussion in 'World Events' started by Quantum Quack, Jan 29, 2020.

  1. billvon Valued Senior Member

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    A virus can survive in any droplet larger than the virus. So yes, it could easily survive in a 10-15 micron droplet.
     
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  3. Quantum Quack Life's a tease... Valued Senior Member

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    It's facinating and quite terrifying when you realise that an infected patient may breathe onto a sheet of glass, producing a fog on that surface simply by the humidity of his breath and know that the virus is present on that glass and in the air around him.

    That merely breathing the air the patient has exhaled is enough to contract the virus.
    Such is aerosol/airbourne transmission for respiratory viruses.
     
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  5. billvon Valued Senior Member

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    Getting much closer! Cool!

    However - humid air (i.e. air without droplets in it, just with a lot of humidity) does not carry viruses. So the fog isn't the issue. It's the actual droplets suspended in the air (i.e. the aerosol) that can cause problems. Usually these are due to coughing, sneezing, snoring etc. There is now some evidence that regular breathing can, in some cases, produce those droplets as well - and can sometimes spread flu when the person is sick.

    https://www.pnas.org/content/115/5/1081
     
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  7. Quantum Quack Life's a tease... Valued Senior Member

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    And that transmission is considered as airborne?
    Water vapor droplets are about 10 microns and can carry viruses as you have already agreed...so please explain what seems to be a contradiction.
    Water vapor(droplets) is humidity... yes?

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    Last edited: Feb 14, 2020
  8. billvon Valued Senior Member

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    No. Humidity is water vapor, which is a gas. If you have a humid (and clear) day there are no droplets.

    However, if the humidity gets high enough, sometimes you get so much humidity that the air gets saturated or even supersaturated - it is carrying more water than it can "handle." When that happens it condenses on _anything_ including dust in the air. As the water condenses on the dust, the dust motes get larger and larger and become visible. When this happens high in the sky they are called clouds; when this happens close to the ground it's called fog.

    You've probably heard that aerosol distribution depends greatly on conditions, and humidity is a huge one. If it's dry out then the person sneezes, expels an aerosol - and it quickly dries up. The viruses dry out and are inactivated. But if it's very humid those droplets last a long time, and can be infectious for a long time.
     
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  9. Quantum Quack Life's a tease... Valued Senior Member

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    ok...
    According to the virologist in the video I posted for virus transmission to be considered as aerosol or airborne it's droplet size has to be 10 microns or less. (capable of transmission generally greater than 6 feet.) Anything larger is considered as direct/contact or indirect.( transmission generally 6 feet and less)

    How does that work in with your explanation?
    For your convenience here it is again:
     
  10. billvon Valued Senior Member

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    Small droplets stay in the air; large droplets fall out of the air. Consider that 300um water droplets are considered "fine drizzle." Small droplets also evaporate very quickly unless the humidity is high.
     
  11. Quantum Quack Life's a tease... Valued Senior Member

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    So clearly this coronavirus transmission is not considered an airborne aerosol?
     
  12. Quantum Quack Life's a tease... Valued Senior Member

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    From what I understand an aerosol transmission are droplets that are carried by the air. Were as direct/contact/indirect droplets are carried by their own momentum.
    There also may be a grey area where the transmission could be both...?
     
    Last edited: Feb 14, 2020
  13. LaurieAG Registered Senior Member

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    465
    From Google:
    BTW, John Hopkins has revised the figures to Infected 64,437 dead 1,383 and Recovered 6,961 so things are back to Infections/deaths decreasing and Recovered/deaths increasing. They changed the deaths from 1,487 back to 1,383 (- 104) so I gather they couldn't really attribute people who died from COPD stage 4 as Coronavirus deaths (very similar lung damage) without finding Coronavirus in their systems.
     
  14. exchemist Valued Senior Member

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    9,155
    No, not "clearly" at all. It is definitely spread by wet droplets, and, since the size of the droplet has no effect on the virus, this will mean that wet aerosols of small droplets should also be infectious. BUT, what we don't seem to know yet is whether this virus remains active after the aerosol droplets dry out. From what I read, many common cold viruses do remain active for a while in aerosols in this state, in what are called "droplet nuclei". Here is a definition of what these are:-

    " small particles of pathogen-containing respiratory secretions expelled into the air by coughing, which are reduced by evaporation to small, dry particles that can remain airborne for long periods; one possible mechanism for transmission of infection from one individual to another."

    Taken from here: https://medical-dictionary.thefreedictionary.com/droplet nuclei
     
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  15. Quantum Quack Life's a tease... Valued Senior Member

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    That's interesting....
    Of course they still do not really know anything conclusive about this virus's transmission and they openly admit it. China is operating on the assumption like most nations that the virus is not an airborne aerosol and international viral contraction experience to date appears to confirm it. But these are only assumptions...that appear to be working and not much else at the moment as far as I can tell.

    The actual situation in China is far from certain..
    Example:
    Australia has only 15 (?) confirmed cases.
    If the virus was transmitted by way of air borne aerosols that number would be expected to be considerably higher by now. It is not. Current quarantine provisions are insufficient for airborne aerosols if I am not mistaken.
     
    Last edited: Feb 14, 2020
  16. exchemist Valued Senior Member

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    9,155
    No this just a wild guess on your part: there is no positive evidence I am aware of against airborne transmission.

    But in any case, from the description I have given, I hope you can see it is a continuum, from droplets through to drying aerosols, to fully dry droplet nuclei, and once fully dry, for how long in the dry state the virus can remain active. There is not necessarily any hard and fast cutoff between these steps. It will be a matter of degree.

    By the way, I don't understand why you think the isolation methods in use would be ineffective against airborne transmission by dry droplet nuclei. The rate of diffusion of droplet nuclei will be limited (they are still a thousand times bigger than the molecules of the gases in the air), so keeping people in a separate facility would greatly reduce the rate of transfer.
     
  17. Quantum Quack Life's a tease... Valued Senior Member

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    One thing that comes to mind is that any one in close proximity ( nursing staff, doctors etc ) would be infected before the airborne droplets dried. Face masks and gloves etc are insufficient in protecting against airborne droplets. Only a positive pressurized hazmat would be.
    This does not appear to be happening.

    Also the spread of infection during the incubation period of 14 days or so would be far more aggressive that what has been observed.
    Our first confirmed case hospitalized 5 kms from where I live, would have infected considerably more people had the virus been airborne before he was even aware he was ill.
     
  18. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    Look, according to the definitive definitions of definitiveness in the case of what is airborne or not, and by that I of course refer to the 1995 documentary “Outbreak”... something is only airborne if it is able to travel through an air-conditioning vent and contaminate someone in a different room that is otherwise supposedly isolated. If it can’t do that, it’s not airborne. Period.

    And the only sure-fire way of preventing the spread is either a dramatic last-minute cure, or simply dropping a thermobaric bomb on all infected areas.
    If this was the future, we’d be suggesting nuking them from orbit... only way to be sure, after all.

    These are the facts, people! Get with the program!!

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  19. Quantum Quack Life's a tease... Valued Senior Member

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    lol
     
  20. exchemist Valued Senior Member

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    Sure.

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    The outbreak on that cruise ship stuck in Yokohama sees to be spreading rapidly among the passengers, but I don't know whether they are confined to their cabins or not. If they are, then it must be either going through the AC, or perhaps via meal trays etc taken from their cabins by the crew. Oh well, this is just idle speculation without enough facts at the moment.

    We will just have to be patient (possibly in all senses

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  21. billvon Valued Senior Member

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    Coronavirus patients generate aerosols through sneezing and coughing - and recent research indicates they may generate aerosols just by breathing. The question is - is there any virus shed into that aerosol? If it's like almost every other virus out there, the answer is yes.

    Next question - how long does it live in that aerosol? If the aerosol is just water, then it likely "dies" as soon as it dries out - very few viruses remain potent after drying out. Is it blood, or sputum, or something else? If so then it may remain moist for longer, since there's a lot of protein and other materials in the aerosol that will keep things moist for a while.

    Next question - what size is the aerosol? Above about 300um and it drops to the floor within a few seconds. Below about 10um it remains in the air - and it dries quickly. In between? You may have something that remains in the air for perhaps a minute and doesn't dry out quickly.
     
  22. Quantum Quack Life's a tease... Valued Senior Member

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    The only bone of contention is semantic but important when discussing specific fields.

    Do you agree with the following:
    If not how so?
    definition:
    Aerosol:
    An aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas.[1] Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog, dust, forest exudates and geyser steam. Examples of anthropogenic aerosols are haze, particulate air pollutants and smoke.[dubiousdiscuss][1] The liquid or solid particles have diameters typically <1 μm; larger particles with a significant settling speed make the mixture a suspension, but the distinction is not clear-cut. In general conversation, aerosol usually refers to an aerosol spray that delivers a consumer product from a can or similar container. Other technological applications of aerosols include dispersal of pesticides, medical treatment of respiratory illnesses, and combustion technology.[2] Diseases can also spread by means of small droplets in the breath, also called aerosols (or sometimes bioaerosols).[3]

    src: wiki
     
  23. Quantum Quack Life's a tease... Valued Senior Member

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    22,119
    Expectorant such spittle is not an aerosol...as it is unable to be suspended in the air and moves primarilly by it's own momentum.
     

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