Cont: The One Covid-19 Science and Medicine Thread Part 2

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Puppycow said:
Just a follow-up comment from a slightly different news source:

Info from the CDC:

Coronavirus may have infected 10 times more Americans than reported, CDC says (Reuters)

Yeah, a lot of us guessed that was the case a long time ago, but they have evidences.



The way that's worded is confusing to me. Can't you estimate the prevalence in the population from the serology testing alone?

So unnamed "senior administration officials" briefed "a small group of reporters" for this story. Why not go on the record?
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The NPR story Atheist linked names Redfield

Redfield estimates that between 5% and 8% of the U.S. population has been exposed. He points to results from communitywide antibody tests and other surveillance measures that point to this range.
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Comes out to an IFR of between .4 and .7%
 
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The Atheist said:
The CDC has also come out and stated they believe infections are under-stated by a factor of 10, with 20M Americans having had Covid to date: https://www.npr.org/sections/corona...ave-had-coronavirus-heres-who-s-at-highest-ri

I think we can be fairly confident that the same applies everywhere, giving a likely mortality rate of 0.5% overall.
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I think that estimate is reasonable. In Australia there have been 7,595 cases with 104 deaths. This gives a death rate of 1.37%. If the USA had the same death rate and the number of deaths is just as accurate as Australia's deaths then the USA would have about 10 million cases. This is 3.7 times the official figure. I think this would be the lower limit of the number of cases. If Australia failed to diagnose some cases (possible, especially in the early days) then this would make the USA cases even higher. Also my estimate would be the number of cases from a few weeks ago.
 
Pool Testing in the US
Now the talk is about pooling up to 25 individual tests into one batch to speed up testing. But this will only work in areas that have a low 1 to 2 percent positive individual test results. More that that positive, will result in doing lots of individual retests (don't know if they retain the individual samples). This will just slow down isolating positive individuals.
 
Samson said:
9800 tests show 1 positive here today.
This does not compute with theories of mass infection.
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I don't think there is mass infection, but the fact that we're catching 1-3 daily at the border now they're testing means some infected people must have got back into the community before testing commenced.

The point has already been made that most people don't infect anyone, and the evidence is very strong that 90% of cases are so mild, or asymptomatic, that they're not found until serology testing takes place.

I'd say we continue to be lucky. If one of the people going out of quarantine untested had been a super-spreader we'd be headed back to level 3 about now.
 
The Atheist said:
I don't think there is mass infection, but the fact that we're catching 1-3 daily at the border now they're testing means some infected people must have got back into the community before testing commenced.

The point has already been made that most people don't infect anyone, and the evidence is very strong that 90% of cases are so mild, or asymptomatic, that they're not found until serology testing takes place.

I'd say we continue to be lucky. If one of the people going out of quarantine untested had been a super-spreader we'd be headed back to level 3 about now.
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Very lucky, I think we got away with it.
 
First I've seen of age v being symptomatic.

Age is a strong factor influencing probability of being asymptomatic after covid infection.

Below age 40, probability of being asymptomatic is 80%
Above age 60, probability of being asymptomatic is 50%

https://arxiv.org/ftp/arxiv/papers/2006/2006.08471.pdf

My comment: These numbers are consistent with the Diamond Princess where approx 50% were asymptomatic. But it's the first breakdown relative to age.

Also of note is the study is base on close contacts of Covid-19 patients. Testing showed that 51% of the close contacts had acquired Covid-19.


Here's an interesting study out of China (financed in part by the US NIH) that showed about half secondary transmission was from people that were pre-symptomatic.

https://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(20)30471-0.pdf
 
Puppycow said:
... Can't you estimate the prevalence in the population from the serology testing alone? ...
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We could except for a few problems.

The serology tests don't yet have a good reliability record.

And there haven't been enough well designed population studies to get an accurate look.
 
Outgoing Chief Medical Officer in Australia Brendan Murphy said estimates on both infections and deaths worldwide are underreported/underestimated.

The ratio has been approx:
80% mild cases;
20% serious cases;
0.1%-1.5% deaths.

(No idea on the least developed countries.)

marting said:
Only 1 out of 123 children that lived with a Covid-19 infected person got the bug in a Swiss study. May be a lot safer to open up schools than we had previously thought.

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(20)31304-0.pdf
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That's an example of why I think we also need to factor in the pre-existing health of the population/individuals.

It still looks to me like we will all get the virus before any vaccine.

The alarming thing to me is not that.

It's how many die from it. Is there a way to completely prevent someone getting it who is at very high risk?

We've learnt a lot so far, and our healthcare systems have been adjusting.

One cool thing I saw:

Mercedes Formula 1 team designed a new CPAP ventilator for COVID-19 ICU patients and made the design open-source. Mercedes have been making 1,000 ventilators a day for the UK.
 
jadebox said:
I wonder though what happens if a kid does get infected at school. How likely is the child to infect others in his family or community? What about adults working at the school?
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Sweden has kept preschools and primary schools open and it has basically not seen any signs that children spread the disease to any significant degree either among themselves or to adults. Teachers and other school staff members are far more likely to infect each-other than being infected by the kids.

There has so far only been one single significant outbreak at a school where a lot of teachers were sick and one of them ended up dying, which eventually had to close prematurely for the summer due to a lack of sufficient teachers. I live fairly close to this school and it was a very exceptional event especially given the low rate of infection in this region.

Teachers are not any more likely to be infected than anyone else.
 
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Arcade22 said:
Sweden has kept preschools and primary schools open and it has basically not seen any signs that children spread the disease to any significant degree either among themselves or to adults. Teachers and other school staff members are far more likely to infect each-other than being infected by the kids.
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That's consistent with the Swiss study. Frankly, I was surprised by the almost non-existent transmission to children. Even in families where a person had Covid-19. There's clearly something different going on.

OTOH, for people 20 or more it seems they are all pretty susceptible to getting the bug. Even though it impacts older people far harder.

Elsewhere it's been reported that pregnant women don't transmit it to their newborns. Even when they may get it themselves. Curious.
 
Skeptic Ginger said:
We could except for a few problems.

The serology tests don't yet have a good reliability record.
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Some do many don't. The FDA has been coming down a some of the hundred plus purveyors of antibody tests that haven't even applied for an emergency authorization. Many of those are crap. Some tests deployed in Japan in a large group that hasn't had Covid-19 has a positive rate of under 0.1% so at least that test had decent specificity. Sensitivity, OTOH, is harder to quantify as there are fewer known positives to test against.
 
marting said:
Also of note is the study is base on close contacts of Covid-19 patients. Testing showed that 51% of the close contacts had acquired Covid-19.
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I'd be interested to know what "close" is - 51% is a lot.

I'm getting the opinion that asymptomatic people aren't doing much infecting at all. Including this:

marting said:
Only 1 out of 123 children that lived with a Covid-19 infected person got the bug in a Swiss study. May be a lot safer to open up schools than we had previously thought.
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Yeah, kids just don't pass it on, which is exactly unlike every other bug in existence. They mostly don't have symptoms, and it doesn't appear that those asymptomatic cases are even passing it on in the family.

marting said:
That's consistent with the Swiss study. Frankly, I was surprised by the almost non-existent transmission to children. Even in families where a person had Covid-19. There's clearly something different going on.
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Bingo!

There is something going on, and we've been saying it from the start - kids should be highly susceptible to a novel virus and they just aren't.

I was reading yet another piece today about other vaccines conferring protection from completely different viruses, in particular, the polio vaccine.

https://www.nytimes.com/2020/06/24/world/europe/vaccine-repurposing-polio-coronavirus.html

Dr. Voroshilova established that the live polio vaccine had an unexpected benefit that, it turns out, could be relevant to the current pandemic: People who got the vaccine did not become sick with other viral illnesses for a month or so afterward. She took to giving the boys polio vaccine each fall, as protection against flu.
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Much earlier, we had MMR and BCG as potential candidates, so maybe it's just being vaccinated more recently is the key? The wide majority of kids have had all their shots, and obviously, the older a person is, the longer it was since they had any vaccine other than 'flu.

Needs more work.

marting said:
Elsewhere it's been reported that pregnant women don't transmit it to their newborns. Even when they may get it themselves. Curious.
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Babies being born with high antibodies would fit into the same scenario above - that being protected from other viruses confers protection.

I gotta admit, I'd enjoy the humour if this could all be solved by giving people a vaccine for something else.
 
It looks like we're about to see how unhindered transmission of Covid goes. USA, India, Brazil, Mexico and many others are returning wildly increasing infections and don't have any more lockdowns to give.

I think the next couple of months may make the first three months look quite tame.
 
The Atheist said:
I'd be interested to know what "close" is - 51% is a lot.
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The link is the full pdf of the study. IIRC, the "close" was people that had spent over 15 minutes closer than 2m as well as people in the same household.

The reference individuals were people that had symptoms, tested positive and were asked to quarantine at home. I suspect most of the "close" peeps were people in the home they stayed in. Details are in the study. I believe few, if any, of the known references were asymptomatic.
 
The Atheist said:
It looks like we're about to see how unhindered transmission of Covid goes. USA, India, Brazil, Mexico and many others are returning wildly increasing infections and don't have any more lockdowns to give.

I think the next couple of months may make the first three months look quite tame.
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I think otherwise. At least in the USA. There's been a big shift towards the younger crowd out having fun at bars. Older folks are still being cautious for the most part. Very different from the early days where a lot of the cases were older people who probably get a more serious case, spread it more easily, and didn't know the consequences at the time.

Now they do. Fewer going to church. Singing in choirs, or playing bingo indoors.

That said, there will still be some crossover where younger people infect their elders. But I believe that will create a smaller death spike than we saw a few months back. Not to say it won't be significant. I expect it will. Just less than the initial spike. And we also have a small benefit from pharmaceuticals. Maybe 25% less deaths between the two known effective agents.
 
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