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  • Covid-19 Transmission Data

    Posted by David Foster on August 26th, 2020 (All posts by )

    …an interesting study from China.  There is a discussion thread at Grim’s Hall.

    The study indicates that the transmission rate to household members where there is an infected member was 10.3%, while the transmission rate to healthcare workers was 1.0%..and the transmission rate on public transportation was only 0.1%.  However, I think there is some ambiguity in how these numbers should be interpreted.

    If you’re so inclined, read the paper, dig into the numbers and their meaning, and comment with your thoughts.


    15 Responses to “Covid-19 Transmission Data”

    1. Brian Says:

      Nothing from China should be taken seriously, of course.

      This study seems in direct conflict with the article I recently shared about transmission in Sweden, where taxi and bus drivers had very high rates. I assume the difference is for passengers who are on for a ride, vs drivers who are on for longer time periods?

    2. Brian Says:

      “The study indicates that the transmission rate to household members where there is an infected member was 10.3%”
      This seems like it can’t possibly be right, based on everything we’ve seen previously.

    3. David Foster Says:

      Brian…could you comment further on that other household data?

    4. David Foster Says:

      The Swedish data is interesting:

      “In the fully adjusted model, the mortality risk for bus and taxi drivers is still substantially higher, but no longer statistically different from IT technicians. When looking at how occupations are related to the death of older individuals in the household in the model adjusted only for sex and age, we find that old individuals co-residing with someone working in the service sector have higher mortality than those co-residing with an IT-technician (RR = 1.56, 95% CI =1.01-2.39). In the fully adjusted model, the mortality risk for bus and taxi drivers is still substantially higher, but no longer statistically different from IT technicians. When looking at how occupations are related to the death of older individuals in the household in the model adjusted only for sex and age, we find that old individuals co-residing with someone working in the service sector have higher mortality than those co-residing with an IT-technician (RR = 1.56, 95% CI =1.01-2.39). In the fully controlled models, we do not find any statistically significant differences..”

      This implies that the ONLY thing that makes the bus & taxi drivers more at-risk than the IT people (who are largely working from home) is some set of factors *other* than occupation. But older people living with someone who is driving a bus or taxi *do* have higher risk, even if you adjust for sex and age, which are they main demographic factors in Covid-19.

      Yet then they say ” In the fully controlled models, we do not find any statistically significant differences.” So what are those additional factors (beyond sex and age) that they are controlling for in this version? (looks again) Can anybody else find an explanation?

    5. Mike K Says:

      The cruise ship data should still be a gold standard, if not the only one. The rate of infection of passengers and crew was about 8% as I recall. 10.3% is close enough.

    6. Anonymous Says:

      So if the societal immunity rate is 80% and household members live in close proximity in a closed space; share food, linens, appliances and bath facilities; share most acquired immunities, and share genetic history (innate immunities); how would the infection rate be only half the expected? Either this is BS data or the societal rate is much lower than speculated. Like maybe 5% susceptibility.


    7. Brian Says:

      David: You’re just as capable of using google as I am, David. It is unfortunate that so much of the “research” one finds comes from China, but it seems like 20-30% are typical, and of course I am going by “my impression from reading the news” I confess.
      “Secondary transmission of SARS-CoV-2 developed in 64 of 392 household contacts (16.3%). The secondary attack rate to children was 4% compared with 17.1% for adults. The secondary attack rate to the contacts within the households with index patients quarantined by themselves since onset of symptoms was 0% compared with 16.9% for contacts without quarantined index patients. The secondary attack rate to contacts who were spouses of index cases was 27.8% compared with 17.3% for other adult members in the households.”

      Here’s a case where country/culture will matter hugely. In America people don’t generally live with adults who aren’t their spouses, so I would suspect the average to be higher than in countries where extended families live together.

    8. MCS Says:

      I don’t find the Swedish study hard to understand or surprising. Older people are at higher risk of dying, not new information. It’s not hard to imagine that a younger person sharing the same home and in contact with many people bringing it into the home at a higher rate than someone with more limited contacts.

      As far as the Chinese study, a retrospective study based on the recollection of the subjects is inherently weak. I notice that none of the authors are M.D.’s. Most of the principal authors are associated with the Guangzhou Center for Disease Control and Prevention and the other one with the School of Public Health, Southern Medical University. The first is a government agency.

      The most interesting line: “This manuscript was posted as a preprint on medRxiv on 26 March 2020.”. So not new information.

    9. Brian Says:

      MCS: “So not new information.” Yes, it was just one example. There are many many others. This is a comment section, not a scientific journal. Too many of the articles are from the spring and from China, I’m not quite sure why we haven’t seen a lot more rigorous studies come out with results from all over the world with better datasets. My inclination is almost to credit politics. Who would want to study this topic right now? You’re going to get sucked into political BS no matter what you find.

    10. MCS Says:

      Rigorous = expensive. Here’s the path: get idea for study, identify possible funding source, write grant proposal, taking into consideration the sensitivities of the funder, await response, answer response,… for as many iterations as it takes for a final answer. Unfavorable: start over somewhere else. Favorable: start jumping through hoops of own institution, human research oversight, etc (they won’t want to hear from you until you have money and they’ll want their cut). Assemble collaborators, finalize study plan, get final approval of oversight. Start study. And then you have to do the work, have it peer reviewed and published. Just publishing can take a year.

      Most steps take weeks that may stretch to months. There are exceptions but they’re rare. Given a couple of years, we’ll be knee deep in more studies that a person could read in a dozen lifetimes. The expression “of academic interest only” starts to come into focus.

      An exception, in theory, are agencies like CDC that supposedly support a standing army constantly studying topics of interest. In reality, most resources are tied up already. They may have to take someone off researching the epidemic of gun violence or vaping to study a real epidemic and that won’t be either popular or politically expedient. Even if they make a quick approval, there are still a lot of steps that have to be taken, forms that have to be filled out.

    11. Phil Ossiferz Stone Says:

      So long as this web site continues to hew wood and carry water for the power-drunk bastards trying to keep us masked, muzzled, and locked in our homes for fear of an exotic flu variety only dangerous to those 65+ years old, it will remain uninteresting. This is not about epidemiology, it is about testing with regulatory bayonets to see what we will put up with.

      Meanwhile, the Hispanic population in Texas continues to grow 9 times faster than the Anglo natives, tens of thousands of rapefugees continue to be unloaded upon our shores and given bus tickets all over the country by Catholic and Lutheran foundations funded with our money, our cities continue to burn, the non-masked mobs continue to have their way with sympathetic local governments creating safe spaces for them, DA’s continue to free the rioters en masse or decline to charge them at all, and cops everywhere continue to violate their oaths by, under orders, standing aloof while billions of dollars of damage are racked up. The Republic of our inheritance is being raped and murdered and its battered corpse is being parceled out to invaders that will persecute your children and hunt your grandchildren. But let’s blather about a nonexistent penance that hit its peak months ago.

      An interesting coping mechanism, but not one worth keeping this place bookmarked. Good bye for now.

    12. Anonymous Says:

      Menace, I meant to type in my fit of high dudgeon.

      But seriously. My God. You have whole sections of the country that are animated in a spirit of ideological and racial fanaticism and this is the best content you can cough up. This is what you’re worried about. Get a freaking grip.

    13. MCS Says:

      One of the things that didn’t happen is the homeless apocalypse. Conventional wisdom was that wuflu would wipe them out. It was certainly plausible. Still waiting for the stories that should practically write themselves.

      The DOJ has released a flock of subpoenas to try to find out how many people really died in nursing homes because of Cuomo’s and the other big four’s policy. I’d bet that not even the CIA can find out how much was spent on protecting the homeless by putting them up in hotels. Especially how much the bill for rebuilding and remodeling will be once they’re gone.

      Sounds like a good attack vector for Cuomo’s next challenger. It might even be worth Trump bringing it up. “Billions to protect the homeless, nothing to protect grandpa.”

      All I’ve heard is that infection rates, when they were measured, were very high without symptoms.

      Negative information can be the most important because it brings into focus what we don’t know and especially what we know that just ain’t so.

    14. Kirk Says:

      The fact that the homeless population is relatively unaffected by this should serve as a bit of a “tell” to the rest of us that the whole thing is highly questionable.

      If Covid-19 was as virulent and deadly as they said it was, then we should have to have been hauling bodies out of all the homeless camps in semi-truck loads. I remain unaware of that having happened, anywhere in the country. Or, have we just not found the bodies, as of yet…?

    15. MCS Says:

      200,000 dead and counting isn’t nothing. It’s not the Black Death either. It’s 0.06% of the population.

      One question is: If it were possible, how much would it be worth to avoid those deaths? The surest way to motivate a howling mob is to posit that the answer should be $X. It does absolutely no good to point out the myriad ways we already put a value on life. The reason is that everyone leaps immediately to the scenario of some government functionary making the determination about themselves or their loved ones. As has been seen in the NHS and their NICE tribunal,this is exactly what happens. If only the general public would exercise the same predictive powers on other subjects.

      In this case, at the outset, there was no way of knowing how severe the epidemic would be and only a vague notion how it might be controlled. No one implementing any of the precautions and possible mitigations had the luxury of more than a rough guess. They couldn’t know how prevalent it already was.

      My own opinion is that it was too far disseminated for the lock downs to do much good. I’m less sure if the restrictions on gatherings will be shown to be effective. I don’t trust a lot of the so called “super spreader” sightings. I especially don’t think that they account for the prevalence in the population at large.

      I’m sure that every possible variation of opinion will be able to find vindication in multiple studies in the months and years to come. The sum total of which will leave us paralyzed by the same indecision and conflicting advice next time.

      We may have a better idea of the cost. What I don’t see is a politician with the courage to say out loud that we just can’t afford however many trillions of dollars a similar response will cost in the future.

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