A highly speculative version of the immunological dark matter hypothesis

The COVID-19 pandemic is thought to began in Wuhan, China in December 2019. Mobility analysis identified East-Asia and Oceania countries to be highly-exposed to COVID-19 spread, consistent with the earliest spread occurring in these regions. However, here we show that while a strong positive correlation between case-numbers and exposure level could be seen early-on as expected, at later times the infection-level is found to be negatively correlated with exposure-level. Moreover, the infection level is positively correlated with the population size, which is puzzling since it has not reached the level necessary for population-size to affect infection-level through herd immunity. These issues are resolved if a low-virulence Corona-strain (LVS) began spreading earlier in China outside of Wuhan, and later globally, providing immunity from the later appearing high-virulence strain (HVS). Following its spread into Wuhan, cumulative mutations gave rise to the emergence of an HVS, known as SARS-CoV-2, starting the COVID-19 pandemic. We model the co-infection by an LVS and an HVS and show that it can explain the evolution of the COVID-19 pandemic and the non-trivial dependence on the exposure level to China and the population-size in each country. We find that the LVS began its spread a few months before the onset of the HVS and that its spread doubling-time is \sim1.59\pm0.17 times slower than the HVS. Although more slowly spreading, its earlier onset allowed the LVS to spread globally before the emergence of the HVS. In particular, in countries exposed earlier to the LVS and/or having smaller population-size, the LVS could achieve herd-immunity earlier, and quench the later-spread HVS at earlier stages. We find our two-parameter (the spread-rate and the initial onset time of the LVS) can accurately explain the current infection levels (R^2=0.74); p-value (p) of 5.2×10^-13). Furthermore, countries exposed early should have already achieved herd-immunity. We predict that in those countries cumulative infection levels could rise by no more than 2-3 times the current level through local-outbreaks, even in the absence of any containment measures. We suggest several tests and predictions to further verify the double-strain co-infection model and discuss the implications of identifying the LVS.

That is a new paper from Hagai and Ruth Perets, another link here, via Yaakov.

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did they consider faked data?

Looks to me they are faking data.

They argue a huge population of a virus, LVS, which has never been isolated, much less gene sequenced, exists without taking any action to find it.

Reminds me of the claims of unseen planets based on claimed perturbations in orbits of visible planets. Eventually Pluto was found, but didn't exactly fit the predictions.

Lots of new viruses are found when anyone looks, but there significance is mostly low. If a virus is found, will it be the one they "predict"? Or just one that seems related.

And there claim is the unidentified virus is present globally, based on their model, so it's not a matter of "China keeping it secret". In fact, they imply it might not have started in China, or at least not Wuhan.

In any case, it's interesting how much is not known about the virus and the multiple diseases it causes in humans, even with so many people focused on writing papers about it for academic and professional advancement.

I think they've been reading too many string theory papers. There are much simpler explanations. The spread through the US, for example, seems to follow classical epidemic patterns with no need to argue for some kind of pre-exposure.

Back when pulsars were newly discovered, a roommate of mine, an X-ray astronomer, wrote a doctoral thesis showing that pulsars could be neutron stars with three X-ray hot spots. The problem, he confessed, was that ANY observed pattern could be explained by postulating three X-ray hot spots.

You can probably explain ANY pattern of epidemic spread by postulating two - or at most three - strains with the appropriate properties. There are just so many other variables, that it isn't sure that this theory adds anything.

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American deaths/7 day rolling average
July 3 626/555, July 4 265/518, July 5 262/515, July 6 378/516, July 7 993/556, July 8 890/585, July 9 960/625

July 10 849/657, July 11 731/723, July 12 380/740, July 13 465/753, July 14 935/743, July 15 1002/760, July 16 963/761

July 17 946/775, July 18 813/787, July 19 412/791

In a "low trust country," what can we do, other than "speculate?"

In a responsive democracy it might be different ..

Anon, you misunderstand prior_approval. He's an expat living in Germany trolling you with the American deaths stats.

Lol Boomers

I think the deaths might actually matter more in the world than the comments.

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"Anon, you misunderstand prior_approval. He's an expat living in Germany trolling you with the American deaths stats."

How can anybody miss that?

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Speculative indeed. So Finland, Austria, and Greece had LVS strains broadly circulating, but Sweden, Germany, and Turkey did not? There are considerably easier explanations for differences between countries in Europe, and those in the Americas. It is difficult to imagine Canada having a LVS 'pandemic' while the U.S. did not.

I don't think so. Greece had a hard lockdown for two months, you needed a police clearance to go shopping, so it's not the same as Sweden, which more or less employed voluntary social distancing. That's why Greece is 10x fewer C-19 cases than Sweden.

From memory--and I have a good memory--the dark immunology thesis is that certain SE Asian countries historically exposed to fruit bats (we have them in our palm trees in our PH country house) have immunity to certain strains of C-19, which makes sense since SE Asian countries have relatively weak health infrastructures (dengue fever for example is common in Thailand; they still have rabies in PH, I got the shot).

Bonus trivia: H1N1-Spanish Flu of 1919 also had several strains, the second strain was deadlier than the first. Second wave coming this fall? Needless to say, C-19 virus is chimeric, doubling the problem since it has a "once-in-fifty-year" DNA profile, being a lab virus (not uncommon with weird chimeric viruses as opposed to natural creations; they've crossed in a petri dish some mouse DNA and DNA from a plant, talk about chimeric?! Little House of Horrors for you musical opera fans)

It's Little SHOP of Horrors, here is the trailer only Boomers can recall: https://www.youtube.com/watch?v=ns46cepKAnU

"Feed me"

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When we lived in Queensland we had fruit bats in our mango tree. Do you mean they might have done us a favour?

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Ray, what then do you propose as the cause for a lack of community transmission in “mainland” SE Asia? Look at Bangladesh right now and across the border in Burma it’s literally a nothing-burger. Same in Thailand, Laos, Cambodia, and Burma. I’m not simply willing to chalk this up to people “wai”-ing at eat other. Have you been to Burma, Laos and Cambodia? They are all overcrowded and have quasi-functioning healthcare systems. Cambodia barely has a hospital in the country that I would trust if my life was in the line. It literally makes no sense.

A relative has access to some of the data in Thailand. After the initial “lockdown” there thousands of people fled out from Bangkok into the rest of the country. Along with this crowd came hundreds of COVID positive people fleeing into the hinterlands. This led to hundreds of hospitalizations in my relative’s area but no local transmission. So much so that COVID is called the “Bangkok disease” at the hospital. It doesn’t appear to spread locally.

While you do have bats in Phil do you have hill tribes? Do those hill tribes stretch from Phil into Southern China like they do in Thailand and the rest of Southeast Asia?

What about bat consumption? Are bats eaten as frequently in Phil as in “mainland” SE Asia?

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Yes speculative and crucially not backed up by medical evidence but then nobody has been looking for a LVS.

It explains so much we can see about Covid but is hitherto inexplicable. Answering Charles, don't think in terms of countries but sub sets of populations within countries.

I have lost count of the number of Canadians from East, West and middle I have met travelling the world.

I very rarely meet mid-Westerners outside of Chicago and the odd Atlantan and Texan. The preponderance of western and eastern seaboard travellers (and indeed inbound visitor numbers) over flyover American travellers is immense.

Similar divisions could well explain why BAME and bottom quartile communities in Europe have suffered at least four times worse than the general populations.

Not finding "LVS" doesn't mean no one has been looking for "LVS".

My guess dozens of researchers are looking for related viruses on an ongoing basis, spurred by the published sequences of SARS, MERS, and others. The search for the predicted planet X continues.

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Also makes sense that Spain may have missed the LVS, given the large distance to China.

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isn't it necessary to assume that LVS is much less deadly as well. Considering that WHO and national networks are set-up to detect cases of influenza-like illnesses, don't we need to assume that LVS is largely asymptomatic?

"isn't it necessary to assume that LVS is much less deadly as well"

That's exactly what they're assuming, and they say so explicitly: that's what "low virulence" means!

"don't we need to assume that LVS is largely asymptomatic?"

The LVS doesn't have to be asymptomatic, it merely has to have mild symptoms that mimic the common cold or a mild flu. So people who become sick with it don't bother going to a doctor, or if they do go to a doctor the doctor assumes it's a standard virus, or if the doctor decides to be exceedingly speculative and run a test, the test will come up empty because it's a novel coronavirus that we didn't have tests for.

All of that works in favor of the LVS hypothesis. As other commenters have said though, it's highly speculative. By now, people have been tested all over the world, where's the evidence for people having been infected with this hypothesized LVS?

It has to be sufficiently different from SARS Cov-2 to be undetectable with our current tests, yet similar enough to provide cross-immunity. That's not impossible but Occam's razor makes this a less likely hypothesis than the combination of mainstream hypotheses we currently have.

OK but wouldn't a LVS strain have an evolutionary advantage over a HVS? The virus doesn't necessarily want to kill, it just wants to spread. Even killing less than 1%, the dead can't spread the virus and killing people causes living people to start wearing masks and take precautions.

If the LVS strain has an evolutionary advantage over the current one AND it also enjoyed a head start in global spreading that doesn't seem to really make sense...if nothing else shouldn't it have been picked up by now?

"The virus doesn't necessarily want to kill"

True, but neither version kills very much and only after the host has had it for weeks. There's not much difference in a virus that's 0.1% Fatal and one that is 1.0% fatal.

"the dead can't spread the virus and killing people causes living people to start wearing masks and take precautions."

Yes, this is certainly true, and if the theory is correct at the end of the day LVS will probably have infected far more people all else being equal.

But to your broader point, this is all speculative at this point.

I defer to Catinthehat below.

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They claim the LVS is less transmissible than the HVS, that's key in their model. They claim the LVS started spreading in China ~ 86 days prior to the HVS ( originating far from Wuhan , maybe close to Vietnam).
In their model some countries (with high mobility exposure to China) i.e South east Asia and China minus Wuhan were exposed to the LVS long enough that when the HVS arrived there, they had already achieved a significant level of immunity which stymied SARS_CoV-2 spread.

Other countries were not exposed to the LVS significantly ( Europe, US) and the HVS spread there overtook the LVS.
As a coincidence , the crucial mutation occured in Wuhan where the cases congregated around a wet market and where there is also a virology lab specializing in zoonotic viruses
The LVS is epidemiologically hard to detect as it causes very mild symptoms.

In essence, then, R0 for the Covid-19 virus was lower in some countries because of pre-existing immunity from the 'dark matter virus' that swep the area before as well as other factors like a mask wearing culture etc. In other countries R0 was much higher because they got the worse of all worlds, no immunity from the mysterious hypothetical 'dark virus' plus no social distancing culture. Other countries had a combination between the two extremes.

yes. It has some explanatory power but at the cost of introducing an ad hoc hypothesis of a hidden antecedent virus that made a jump in virulence and transmission in Wuhan.
I do think also that South East Asian countries culture and effective early measures made a lot of difference.

So sounds good but a bit like 'Planet X' let's see if someone actually comes up with a virus and its DNA...which should not be very hard.

BTW someone should be sampling viruses on a regular basis.

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yes, they assume that it produces very mild symptoms, easily associated with a mild cold and has a lower Ro, so not looking like a concerning epidemic,
No cause for a WHO to get alarmed so it can be undetected.
It's not implausible. It's a "hidden variable " theory with the LVS purporting to explain the heterogeneity.
however not all -not implausible- theories are true.
It might be hard to find it now to prove/disprove this theory because in SE Asia it might be extinguished and in the US/Europe , it hasn't taken hold after the lockdowns.

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Basically never causing death, no symptoms, and to complete the trifecta, similar enough to SARS-COV2 to generate an immune system response, but dissimilar enough to not be detected by either PCR or antibody tests.

Not impossible, just so unlikely as to be a minor matter, compared to the U.S. finally putting together a testing regime that would help prevent the HVS version from spreading.

The small problem is that the U.S. was testing as much as South Korea, Canada. the U.K. and Sweden in late March and 20 times more than Japan. Germany was testing three times as much but still low.

By mid April, the U.S. was closing the testing gap with Germany, tested somewhat more than Sweden and 4 times as much as South Korea and Japan.

By mid may, the U.S. was testing 30% more than Germany, and about the same as the U.K. and Italy while testing while testing 5 times as much as South Korea and 20 times as much as Japan.

Leaving aside the obvious fact that any country with a few hundred new cases a day is going to be testing much less than a nation with 20,000 a day (about the lowest number of new cases in the U.S. since the end of March), the problem is timely results. And the U.S. is having a real serious problem with that, as it takes days for results to come back in many of the states experiencing the sharpest rises in cases. Further, with a positivity rate of 20%, it is clear that the number of tests being given is far too low to actually track growing spread.

The sad thing is that in mid May, Germany had around 750 new cases a day - the U.S. had 20,000. That the U.S. was only testing 30% more is just further evidence of how completely inadequate American testing was then. And now, with 60,000+ new cases a day, the American system is starting to fall apart - again. It should not be hard, in the second half of July, to point out just what an extreme outlier the U.S. is concerning this pandemic.

Only Japan and South Korea are in a lower cases per capita group. We were constantly told South Korea was doing "massive testing to control the virus" while America was way behind other countries when that wasn't the case. The U.S. was testing as many people per capita as Korea was and 20 times as many as Japan in late March and note that the U.S. has had per capita 75 times as many deaths as South Korea and 60 times as many deaths as Japan.

You seem to have precisely the same confusion as someone I was talking to yesterday from Alabama. The totals are not relevant when talking about new infections. If Alabama has 68,857 cases, and Italy 244,624, the number that counts now is something along the lines of the 7 day average of new cases in the past week - Alabama is at 1777, and Italy 196. This does not take into account the fact that Alabama has only a twelfth of the population.

Alabama is currently experiencing a wave of infections that is both larger than Italy is experiencing now, and on a per capita basis, greater than anything Italy ever experienced at all, adjusted for population - Italy's highest seven day average peaked around 5500 (with a single day spike above 6000) - roughly a third of the actual case count in Alabama right now.

Of course this does get back to testing, comparing numbers at different times, etc.

However, what happened in April is not particularly important when looking at what is happening right now.

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"It should not be hard, in the second half of July, to point out just what an extreme outlier the U.S. is concerning this pandemic."

The U.S. is typical for a large Western country. Deaths per capita:

Denmark......0.0001
Germany......0.0001
Canada........0.0002
U.S...............0.0004 (will be 0.0005)
France.........0.0005
Italy.............0.0005
Sweden.......0.0006
Spain...........0.0006
Belgium......0.0008

Also rans:

Australia....0.000005
S. Korea.....0.000006
Japan..........0.000008

At no point did I mention deaths, just new infections. The U.S. is an extreme outlier in that regard.

One hopes that deaths will not rise at the equal rate of new cases, because that would be a true catastrophe for America. And sadly, the U.S. has a higher current number of deaths than all of Western Europe combined (full disclosure - I did not check 30 odd countries, but deaths rates in Italy, the UK, Spain, Germany and Sweden do not even add up to 100 in a day). This is another example of the same flawed reasoning. The pandemic is (currently) checked in Western Europe - it is not checked in the U.S. Making a historical per capita comparison today is not particularly relevant when the rate is still growing in the U.S.

I didn't make a historical per capits death comparison considering the data is from today, and I added that the U.S. will reach 0.0005. (and not go higher).

I forgot the U.K. ....0.0007

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Ah, yes, the Second Gunman Hypothesis. Not impossible, to coin a well-worn phrase. But what affect will it have on the willingness to take the vaccine. Yes, the freedom not to wear a mask, the freedom not to practice social distancing, or, the granddaddy of all freedoms, the freedom not to take the vaccine. Heterogeneity for me, vaccine for thee.

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Tyler, I have yet to read the paper. Based only on the abstract, let me ask you why you take seriously studies in which countries are the relevant analytical units. To choose countries because they have data is grotesque (even assuming they have reliable and relevant data on what the analysis is about). Please stop this nonsense.

Last month you have a post with a long email sent to you about research. In the final line, the author warned readers about the streetlight effect (seehttps://en.wikipedia.org/wiki/Streetlight_effect). You have been ignoring this warning for a long time.

I can understand not seeing them as relevant in 1920, when many countries and borders were arbitrary lines on the map and people went about their lives without paying them much heed, but generally, global increases in state capacity in recent decades have made them much more relevant analytical units than in the past. In most areas of the world, national borders serve as strong discontinuities for everything from travel choices to health policies to nutritional levels.

Take a location like Mohancun, Yunnan, where China, Myanmar, Vietnam, Laos, and Thailand are closest together. Draw a circle of 180km radius. 100 years ago, perhaps as recently as 50 years ago, the life prospects and epidemiology of anyone in that 180km radius was (compared to today) roughly identical - agrarian, subsistence, poorly educated, no state penetration, poor access to medical services, etc. Today, you have 5 distinct areas with large variations in all of the above, as well as patrolled and regulated border crossings. And the primary discontinuity is not the mountain rangers or rivers but the national borders. The notable exception, Mong La, Myanmar, is due to it being effectively annexed into Chinese administration of infrastructure and services.

In the same way that Benedict Anderson outlines the formation of distinct nationalisms and identities formed by the rigidization of borders and the expansion of state power into the realms of education and literature, so too do you get the rise of nation-states as distinct analytical units due to the expansion of state capacity, policy, service, and customs.

Please correct me if you think I'm mistaken.

Yes, I agree with you. State capacity has been expanding in many countries and today we know a lot more about countries than ever. We can list countries according to some basic dimensions --say, territory and population-- but we cannot explain why the territories and populations of existing countries differ so much (as the late Alesina and some of his colleagues used to ask: Why are there so many countries?). It's not surprising then that even if we agree that state capacity has expanded we cannot explain the persistence of uneven state capacity across countries. The same happens with the uneven increase in the number of COVID-19 cases across countries. The same happens with so many other changing dimensions unevenly distributed across countries.

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This would explain a lot about Southeast Asia - Laos, Cambodia, Thailand, Vietnam, including the claim of 90% asymptomatic cases in Thailand - but then I wonder why the LVS wouldn't have spread much in China and why then Wuhan was so vulnerable.

It really takes very little thought to see how this idea founders on the rocky shores of what we actually observe. It would be much more fun if we were looking for LVS phlogiston instead of dark matter.

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Am I the only person that’s here for the economics, enjoys the occasional travel/food/whatever, but is getting a little tired of the “speculative/high speculative” and other COVID related posts that our hosts throw up, triggering the same rapidly aging arguments ?

Feels like a four year shaking an ant farm to watch the fight.

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Cowen has been pointing to heterogeneity since the outset of the pandemic, and he isn't going to back down now. The point I have tried to make is that small differences in actions can lead to large differences in outcomes. I suppose that's a form of heterogeneity, but I'm not sure if that's what Cowen has in mind when he uses the term heterogeneity. I've assumed that he is referring to heterogeneity among individuals, some have stronger immunities than others, some have antibodies that others don't, etc. That there may be two very different strains of the coronavirus is not impossible (just like the Second Gunman Hypothesis), but it can become a huge distraction, cause a diversion of resources, and contribute to resistance to the vaccine. Both Cowen (through Fast Grants) and Tabarrok (through his tireless and many efforts to increase funding for vaccine research) have done great work, but my observation is that Cowen is more willing to raise speculative issues while Tabarrok remains focused on one goal, the vaccine. We won't know until the end who made the more valuable contribution.

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Real time peer review has its limits: It's hard to unring the bell. "That is why we and a group of over 100 scientists are calling for American scientists and journalists to join forces to create a rapid-review service for preprints of broad public interest. It would corral a diverse contingent of scientists ready to comment on new preprints and to be responsive to reporters on deadline. This would provide journalists reliable access to independent scientists to help deal with today’s growing stream of preprints." https://www.nytimes.com/2020/07/20/opinion/coronavirus-preprints.html

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A great big yawn on this paper. The fun thing about running a daily Newsletter is that I get to read a lot of models. I have probably read well over 150 to date. They range from good to bad with a lot of indifferent ones in between. One can try to prove anything with a model as they are just that, a model! I remember reading one two weeks ago from Carnegie-Mellon/a> that predicted very little out break during the summer months.

My model is very simple: SARS-CoV-2 is here and we need to deal with it!

Sorry about screwing up the hyperlink. :-)

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I agree. We may have blown the first round, but we don't *have* to count ourselves out.

As anyone knows who places high trust in its guidance, public choice theory has already clearly demonstrated the failure of America to get to grips with controlling the virus.

Time to make a falsifiable hypothesis - America will not do any better in round two. Assuming you think that America is not still on round one, having never 'flattened the curve' in the first place.

For fun, compare NY state to another nation noted for its failure to handle the pandemic well. Yesterday's seven day average UK / NY new cases 621 / 932, UK / NY deaths 69 / 24. Now the kicker - the UK has more than 3 times the population, and those numbers are not per capita. In other words, deaths per capita in the past week are essentially identical.

Shrug. I don't know why this kind of momentous question is not "political economy"

As Trump Ignores Virus Crisis, Republicans Start to Break Ranks

but I guess the "public choice" tautology is that leadership cannot matter, because leadership never matters.

Under the leadership of a leading economist, Fast Grants shows how effectively a non-profit can participat4e in fighting a pandemic.

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"It matters who runs Tesla or Facebook, but it doesn't matter who runs the United States of America." Shrug.

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This seems a strange comparison. Both are doing quite well now that their peak is long over.

The U.S. certainly did flatten the curve, no denying that with straight face. And the second peak looks to be approaching, probably this week.

From the April peak to the May trough was not even a 50% reduction in new cases before cases started rising again in mid June, to now be about twice as high as the April peak.

Flatten the curve does not have much of a definition, but there is no question that the U.S. never had the disease under control, and anyone who thought in May that the case numbers would decline further was very mistaken.

Deaths, 7 day average:
April 15 2187
May 15 1562
Today 791

And from the comment above -
July 3 555
July 10 657
July 17 775
That is close to a 50% increase in three weeks. And if the trend continues at an increase of 125 per week, it will take less than 7 weeks to be back to the May 15 total.

And why would you skip June 15 at 758?

The increase in U.S. deaths was sudden from July 7, which makes no sense after very slowly declining from late April. The only thing that explains a sudden sharp increase is that deaths from previous weeks were added more than usual. Also, the seven day rolling average shows the increase in deaths has stalled.

July 20's seven day average is 802 - on July 13 it was 753. Unless you consider you consider a more than 5% rise in a week stalling, the increase continues.

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How high are the GRE scores of the authors?

Yes of course the ability of the authors matters, but at this stage int heir career one would hope their reputation provides more information than their GRE score

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Speaking of speculative cross-protection, in the Indian state of Tamil Nadu, older adults 60+ will be administered BCG vaccine, in the hopes of moderating their course of disease should they be infected.

https://twitter.com/Vijayabaskarofl/status/1283322601381588992

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This is what modeling is for, to see what might underlie the data. The simple well mixed models are failing (unless tuned day to day which is pointless). Could be a good model for the Western USA but a different one is needed for the highly mixed Mexican population on both sides of the border. (lots of transborder traffic quite legally even up to today).

The extreme lockdown crew fails to heed the old military maxim of not sending your troops where the enemy isn't. Locking down California when the newer virus strain was not around, simply imposed a huge economic loss and achieved little in public health.

"the old military maxim of not sending your troops where the enemy isn't"

Correct, but the flip side of that is not assuming that the enemy isn't there. Because sometimes it turns out that they are there. German panzers traveling through the Ardennes. Stonewall Jackson appearing out of the woods on the Union right flank at Chancellorsville. Japanese plaines from the empty Pacific Ocean attacking Pearl Harbor. Or in modern times, insurgents and IEDs in Iraq.

Sometimes the enemy is in plain sight yet still unaccounted for: Parthian horse archers at Carrhae (who annihilated Crassus's Roman army; cavalry and missile troops were thought to be inferior to the mighty Roman heavy infantry); similarly English longbowmen at Agincourt and Crecy. Hannibal's wings of light cavalry at Cannae, that eventually encircled the Romans. The Iraqi insurgents somewhat fit into this category as well as the hidden surprise category.

If we magically know in advance where the enemy is and where they are not, then life becomes a lot easier. But that's not how things are; in that sense life is more like poker than a chess game.

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Has anyone modeled the hypothesis that heat and humidity inhibit viral spread in the absence of indoor air conditioning being prevalent? Combined with strong public health measures, such as contact tracing in rich areas like Singapore, such a model would account for low spread in much of southeast Asia and the higher spread in places like Florida and Arizona.

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How does Italy fit into this story?

Does Italy specifically have high-traffic between Lombardy and Wuhan/Hubei but no real link to other parts of China? I recall specifically that the Italian universities full of Chinese citizens was fingered as the probable inception point of their outbreak.

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A danger this raises. Normally viruses become less deadly as time goes on. A dead host cannot spread a virus as easily as a live host, after all.

But the incentives for evolution can turn against our interests easily. If a virus is presented with a mutation that makes it *more* deadly but gives it a longer period of time during which infected hosts can pass on the virus, then that mutation would have an advantage over the nicer version of the virus.

Of course a massive increase in deadliness would run into some limits. A mutation, say, that increased deadliness to 40% but allowed a month or two of passing the virus before the victim gets really sick would be so over the top that it probably wouldn't get very far. But increase the infection fatality rate from 0.6% to 2-3% in exchange for a longer incubation period and you're talking massive amounts of death. By playing games with hypothetical 'herd immunity', we are playing with fire.

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While I'm inclined to be dismissive of the two virus hypothesis, there is evidence of immunological "dark matter". Recovered SARS patients, for example, mount an excellent immunological response to COVID, in vitro. Many people who have never had COVID also produce antibodies; the current theory being that this is immunity to related coronaviruses.

I could be open to it but I would expect someone to find this mysterious virus before long given the amount of attention this is getting.

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