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  • Virus Transmission Modes

    Posted by David Foster on May 11th, 2020 (All posts by )

    Here’s an article with data…or at least assertions…about various ways in which Covid-19 spreads and their relative risks.

    To the extent that data at this level of detail can be obtained and verified, it seems a lot more useful than generic claims about lockdowns and social distancing, or the elimination of same.

    Mike K, any comments?

     

    25 Responses to “Virus Transmission Modes”

    1. Mike K Says:

      Lots of estimates and assumptions. The methods of transmission sound reasonable but are also mostly estimates.

      Her assumption that the number of deaths will double after the lockdown is eased is worst case, I think. The cruise ship experience suggested that 20% of those exposed contract the virus. That is becoming a number in New York City. 21% are positive for antibody.

      Georgia is opening up and cases have not increased. High viral loads are a valid issue, which is why NYC is going to have trouble easing.

      My wife is high risk with high IgE immune deficiency but she also has rheumatoid arthritis and has been taking HCQ for years for it. The European experience, I have read, is that of 60,000 people taking HCQ, only 20 have contracted the virus and none were critical.

      I guess we will see as the country cannot afford the continued quarantine.

    2. David Foster Says:

      Mike, one thing I was wondering about is the *time factor* in viral loading. He says that 1000 viral particles in one breath is equivalent to 100 particles in each of 10 breaths…but what if the latter case is stretched out over significant time? For example, say it’s 100 particles on Monday, 100 more on Tuesday, and so on. Intuitively, it seems that the accumulation wouldn’t go on forever, that there’s be some kind of decay curve, but…

    3. The Dark Lord Says:

      author is focused on infections and ignores WHO needs to be infected for deaths to go up … too many assumptions and guesses … almost no science about covid19 …
      another “expert” in the lab … just what we don’t need …

    4. David Foster Says:

      DL…I give him credit for attempting to disaggregate the problem into components…I thought the points about Speaking vs Singing, for example, were worthwhile though probably obvious once you think about it.

    5. Mike K Says:

      I bought a Virology textbook, as mine was years old. The author is the guy who does the weekly podcast I have been listening to.

      This is the podcast, which is interesting.

      Again, these are scientists and not necessarily the best on economics. It’s too bad the efforts on a vaccine were stopped after SARS burned itself out in 2003.

      Middle East respiratory syndrome coronavirus (MERS-CoV) is the second novel zoonotic coronavirus to emerge in the 21st century and cause outbreaks of severe respiratory disease. More than 2,200 cases and 800 deaths have been reported to date, yet there are no licensed vaccines or treatments. Coronaviruses encode unique accessory proteins that are not required for replication but most likely play roles in immune antagonism and/or pathogenesis. Our study describes the functions of MERS-CoV accessory proteins NS4a and NS4b during infection of a human airway-derived cell line. Loss of these accessory proteins during MERS-CoV infection leads to host antiviral activation and modestly attenuates replication.

      That is an interesting quote from a paper linked at one podcast, Fortunately, MERS is still limited in geography.

    6. David Foster Says:

      This article is also interesting…he is asserting that herd immunity is reached much earlier than the standard analysis would suggest. Haven’t read it thru in depth, but I think he is basing this on a range of individual differences in susceptibility to infection and propensity to infect others.

      https://judithcurry.com/2020/05/10/why-herd-immunity-to-covid-19-is-reached-much-earlier-than-thought/

    7. C Gooby Says:

      Good Post, again. I agree with Dark Lord that more lab “experts” interpretation does not make fact, but this is science….work the lab until a reasonable conclusion can be agreed upon. It’s not exact-science, but science..right?

    8. MCS Says:

      I read through to the author’s C.V. and will assume that the numbers he cites are correct. Most of his discussion is irrelevant to trying to figure out where we are headed.

      He cites the famous restaurant case. It largely falls apart if you assume that one in five of the people in the room were already infected. We still don’t know how many people are already infected and possibly infectious, How many were infected and are probably immune and what the difference is between the 20% that were infected in New York and the 80% that aren’t.

      When evaluating the particle spread, the initial velocity doesn’t matter much. The particles are both low density and low mass with a really poor ballistic coefficient. All but the very biggest are drifting in the air within a foot or two and all but the very smallest headed for the floor. There is also the effect of dilution that increases at 4/3 the cube of the distance for those of us living in spherical rooms and twice the cube for rectangular rooms. This is probably why six feet is used as a reasonable distance rather than the farthest that anyone can imagine a perfect hypothetical particle traveling under ideal conditions.

      We don’t, and Trump doesn’t need to know what is possible. We need to know what IS. From that we would have a chance of judging what is likely to happen. This seems to me to be what the CDC should be doing but is resolutely ignoring.

    9. Mike K Says:

      Here is an interesting study of employees of major League Baseball.

      This shows the prevalence of positive antibody testing,. The positives is very low compared to the general population.

      This is a working population agewise. Middle class. They have been following the rules.

      Might be a negative for a “second wave” experience.

      There is no way to keep the lockdown until a vaccine or the end of the epidemic.

      Contact tracing is not going to work either.

      Sweden results may represent voluntary precautions.

      Lockdown will NEVER end the virus, only delay. Most transmission is indoors. Extended contact.

      Iceland study: No instance of transmission from a child to parent.

      Only therapy mentioned is vaccine or remdesivir. What about HCQ ?

    10. Sconnie Says:

      https://covid19criticalcare.com/wp-content/uploads/2020/04/MATHPressRelease.pdf
      Toolbox using readily available therapies

    11. MCS Says:

      This has got to be the most incredibly stupid media piece I’ve seen on the pandemic.

      The health authorities in Florida apparently wasted time planning instead of spreading mindless panic in mid-February.
      https://www.msn.com/en-us/news/us/florida-knew-a-covid-19-pandemic-was-likely-state-leaders-didn-t-warn-the-public/ar-BB14nF9U

      How dare they. The stores could have been emptied of bread and toilet paper weeks earlier if they’d have been on the ball.

    12. Jonathan Says:

      DeSantis looks like a contender for the 2024 Republican presidential nomination, and not only because of his competent handling of the epidemic. We should expect to see many more articles along similar lines as that MSN piece.

    13. MCS Says:

      Hope you’re right, the Republicans need more new, good candidates. I had high hopes for Scott Walker but he flamed out awful fast.

      What we don’t need is another Jeb. He was a decent governor and a decent man but he was like Chamberlain at Munich when it came to dealing with the media and the Democrats.

    14. Mike K Says:

      DeSantis is doing a good job,. I think Nikki Haley is angling for it but I don’t know how strong she was a SC Governor. Obviously the Dims will have a female. Pence seems to me to be weak. He folded on the Religious Restoration Act when Governor.

      I kind of like Rand Paul. Hopefully, foreign policy aside from China will be less important.

    15. MCS Says:

      It’s not like there’s some sort of law that Walker couldn’t run again. I suppose it comes down to if he wants to bad enough and money.

      Haley is probably handicapped by having a fairly uneventful term, at least from here. You’d think that would count as a plus. I’m not sure what her time in the UN did for her foriegn relations expertise. It’s not like anything is accomplished there.

      I’m willing to consider anyone. Not a Senator. Has actual, real world accomplishments. Is able to clearly state one or two guiding principals that I can live with and stick to them. Doesn’t try to sell any 38 point plan to do anything.

      Of course, Romney would have qualified so there’s probably something I’m missing.

    16. Mike K Says:

      I liked Walker early on but I think his money early on was coming from the Koch brothers who have now allied with Soros.

      I don’t think that is a good look.

      A defender of internet censorship with ties to one of China’s largest tech companies moderated a panel Thursday at a new think tank funded by Charles Koch and George Soros.

      Whoops !

    17. MCS Says:

      The Koch’s money is spread out in an awful lot of different places. I’m not convinced by one speaker at one event sponsored by one group that takes money from both. If, and a big if, Walker wants in, I’ll listen to what he says with that in mind.

    18. miguel cervantes Says:

      these oligarchs seems to be likeminded, Koch and elements of the Scaife foundation, did fund the Clarence Thomas documentary, so there is that. the mercers had to be forced from renaissance technologies, because they were funding okeefe and other parties, oracle splits his take between trump and Bernie,

    19. MCS Says:

      Now something really interesting:
      https://justthenews.com/politics-policy/coronavirus/study-suggests-majority-population-may-already-have-some-degree

      And here’s a pre-proof copy of the paper:
      https://www.cell.com/action/showPdf?pii=S0092-8674%2820%2930610-3

      It, according to the summary on Just the News, reports finding T cell responses to the Wuflu from samples collected years ago in 40-60% of the population. It’s about to be published in Cell which is considered a leading journal.

      The bottom line is that a large proportion of us were already partially protected which may be the reason that there are so many asymptomatic to very mild infections.

    20. Mike K Says:

      MCS, that journal article suggests that SARS-2 the WuFlu virus is similar enough to other corona viruses that some cross reaction immunity exists. That might explain the low percentage infected in the cruise ship experiment.

    21. David Foster Says:

      Here’s a breakdown of Coronavirus risk versus age, with comparisons to flu/influenza fatalities and transportation accident deaths:

      https://www.bloomberg.com/opinion/articles/2020-05-07/comparing-coronavirus-deaths-by-age-with-flu-driving-fatalities

      Using the midrange estimate of 200,000 fatalities over the course of the epidemic, the risk for people in the 45-54 age range is 25 per 100,00 population. For the 45-64 group, it is 58 per 100,000.

      As a comparison, the occupational risks of some trades generally considered as dangerous are:

      Structural Ironworkers 24
      Roofers 51
      Commercial Fishermen 77
      Loggers 97

      The recent CDC ‘best estimate’ numbers look considerably higher than these, though it’s hard to compare because the age breakpoints are different.

    22. MCS Says:

      One difference is that to be classified as a logging death, the decedent actually had to be engaged in logging rather than merely a resident of a state where logging was taking place. Also not counted are loggers killed in traffic accidents on their way to church or slipping in the bath tub.

      We’ll know that they’ve given up on milking this thing when people are allowed to die of anything else.

      I’m a survivor of 30 years in agriculture and not impressed.

    23. David Foster Says:

      MCS…given that there are deaths being counted as Coronavirus that are really something else…how much is that realistically skewing the numbers? Is it really likely that it is more than, say, a 20 or 30% difference?

    24. Gavin Longmuir Says:

      MCS: “We’ll know that they’ve given up on milking this thing when people are allowed to die of anything else.”

      Tasteless Joke of the Year, with apologies to everyone:

      Authorities in Pakistan have reported that no passengers died from the recent crash of an Airbus A320 in Karachi — they all died from Covid-19.

      I will leave now.

    25. MCS Says:

      your guess is as good as mine or literally anyone’s. That’s the problem with bad data. From now on, any conclusion drawn using it is just another opinion. I can adjust it one way and you another and use it to support whatever argument we wish to make.

      I’ve read estimates that the normal error rate for allocating mortality is already a third. When it’s used to support some reasonably benign health intervention, it probably matters little. When it’s the reason for shutting down a large portion of the economy, it matters a great deal.

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