Month: August 2020

Which time lags matter for testing regimes?

What determines the success of a COVID-19 Test & Trace policy? We use an SEIR agent-based model on a graph, with realistic epidemiological parameters. Simulating variations in certain parameters of Testing & Tracing, we find that important determinants of successful containment are: (i) the time from symptom onset until a patient is self-isolated and tested, and (ii) the share of contacts of a positive patient who are successfully traced. Comparatively less important is (iii) the time of test analysis and contact tracing. When the share of contacts successfully traced is higher, the Test & Trace Time rises somewhat in importance. These results are robust to a wide range of values for how infectious presymptomatic patients are, to the amount of asymptomatic patients, to the network degree distribution and to base epidemic growth rate. We also provide mathematical arguments for why these simulation results hold in more general settings. Since real world Test & Trace systems and policies could affect all three parameters, Symptom Onset to Test Time should be considered, alongside test turnaround time and contact tracing coverage, as a key determinant of Test & Trace success.

That is from a new paper by Ofir Reich.

The U.S. selects better for Asian immigrants than does Australia

Whereas Australia has pursued a skills-based migration policy, the United States has privileged family-based migration. The key contrast between these migration regimes provides a rare test of how national immigration policy shapes immigrant selection and integration. Does a skills-based immigration regime result in a more select group of Asian immigrants in Australia compared to their counterparts in the United States? Are Asian immigrants more integrated into their host society in Australia compared to the United States? Focusing on four groups of Asian immigrants in both countries (Chinese, Indians, Filipinos, and Vietnamese), this article addresses these questions using a transpacific comparison. Despite Australia’s skills-based immigration policy, we find that Asian immigrants in Australia are less hyper-selected than their counterparts in the United States. Asian immigrants in Australia also report worse labor market outcomes than those in the United States, with the exception of Vietnamese—a refugee group. Altogether, these findings challenge the conventional wisdom that skills-based immigration policy not only results in more selected immigrants, but also positively influences their integration into the host society.

That is from a new piece by Van C. Tran, Fei Guo, and Tiffany J. Huang, via the excellent Kevin Lewis.  The mix of offering a large potential market, and not so much welfare, is a significant part of the U.S. immigrant selection mechanism.

Coming soon, to a country near you

But let’s start with the UK:

The number of people in hospital with Covid-19 has fallen 96% since the peak of the pandemic, official data reveals.

Hospital staff are now treating just 700 coronavirus patients a day in England, compared to about 17,000 a day during the middle of April, according to NHS England.

Last week, some hospitals did not have a single coronavirus patient on their wards, with one top doctor suggesting that Britain is “almost reaching herd immunity”.

In a further sign of good news, the virus death toll in hospitals has also plummeted. On April 10, the day the highest number of deaths was announced to the nation, NHS England said 866 people had died. On Thursday last week, there were just five hospital deaths across the entire country. It represents a fall of more than 99% from the height of fatalities during the crisis.

Note that the pubs and many other venues have been open for over a month, and social distancing protections in the UK remain relatively weak, nor has individual or political behavior in the country been especially responsible.

Here is the Times of London piece (gated).

Monday assorted links

1. How safe is it to fly? (Bloomberg)

2. What is the share of the population with preexisting immunity?  Recommended.

3. And excellent David Wallace-Wells piece on the spread of herd immunity ideas and T-cell immunity (as more significant than had been thought) throughout the scientific community.  Also recommended.

4. Obesity and corruption.

5. Male earnings in the U.S. do not show a general volatility increase over the last 30 years.

The Contemporary Impact of Black G.I.s in Europe in WWII

Abstract: Can attitudes towards minorities, an important cultural trait, be changed? We show that the presence of African American soldiers in the U.K. during World War II reduced anti-minority prejudice, a result of the positive interactions which took place between soldiers and the local population. The change has been persistent: in locations in which more African American soldiers were posted there are fewer members of and voters for the U.K.’s leading far-right party, less implicit bias against blacks and fewer individuals professing racial prejudice, all measured around 2010. Our results point towards intergenerational transmission from parents to children as the most likely explanation.

from a new paper by David Schindler and Mark Westcott in ReStud. Black GI’s also experienced a society with much less segregation than in the United States.

Mixed race couples dancing in a London club, 1943. Original Publication: Picture Post – 1486 – Inside London’s Coloured Clubs – pub. 1943 (Photo by Felix Man/Picture Post/Getty Images)

Mixed race couples dancing in a London club, 1943. Original Publication: Picture Post – 1486 – Inside London’s Coloured Clubs – pub. 1943 (Photo by Felix Man/Picture Post/Getty Images)

From this review.

Rapid Tests

Here’s a good picture illustrating the difference between the PCR and Rapid Test. A PCR amplifies DNA and so if taken at the right time it will detect the virus before a rapid test will. But this happens when there isn’t much viral load and too little of the virus to be transmissible. Moreover, at these times, the virus is increasing rapidly so the rapid test will find the virus tomorrow. The PCR test will also pick up fragments after transmissiblity has passed which also isn’t very useful. A rapid test is very sensitive for doing what it is supposed to do, identifying periods of infectiousness.

Michael Mina has done a great job promoting rapid tests and I do think we are beginning to see some recognition of the difference between infected versus infectious and the importance of testing for the latter. What is frustrating is how long it has taken to get this point across. Paul Romer made all the key points in March! (Tyler and myself have also been pushing this view for a long time).

In particular, back in March, Paul showed that frequent was much more important than sensitive and he was calling for millions of tests a day. At the time, he was discounted for supposedly not focusing enough on false negatives, even though he showed that false negatives don’t matter very much for infection control. People also claimed that millions of tests a day was impossible (Reagents!, Swabs!, Bottlenecks!) and they weren’t impressed when Paul responded ‘throw some soft drink money at the problem and the market will solve it!’. Paul, however, has turned out be correct. We don’t have these tests yet but it is now clear that there is no technological or economic barrier to millions of tests a day.

Go yell at your member of Congress.

Three areas where you never run out of great books to read

Those three areas are:

1. The history of the British Isles

2. The history of the Jews, and

3. The history of World War II

Each area has attracted remarkable talent, mostly in English I should add, and you can always read yet another great book in these areas, even if you already have consumed many stellar offerings.

Whether you should double down in these areas, or strike out and diversify into the many other areas with lower quality expected return, is in fact a key question when it comes to how to read.

(Of course, a small number of books cover all three areas, though I would not suggest that they get triple credit.)

Are there any other such areas I am missing?  Somehow American history does not do it for me — too much stupidity, repetition, and needlessly “clampdown patriotic” perspectives.

“Israel Versus Anyone”

That is the title of a new research paper by Kenneth S. Brower, focusing on the capabilities of the Israeli military against various potential adversaries.  I do not myself have particular opinions on these questions, but I found this piece interesting throughout.  Here is one excerpt:

The simple and unarguable truth is that for decades the US military has lacked the ability to quickly project conventional ground and air forces into the Middle East that would be able to successfully defend Israel. This has been true for about 50 years.

The US Army and US Marine Corps combined now have an active force structure of just 39 maneuver brigades, of which only about 13 are combat ready. It would require many weeks to bring a portion of the remaining 26 active maneuver brigades to combat ready status. Achieving this would require cannibalization of about 25% of the remaining active units in order to bring the others to full strength. US reserve National Guard maneuver brigades would each require about five months for mobilization, retraining, and deployment. These National Guard reserve units are thus irrelevant to any Israeli rescue scenario.

The ability of the US military to deploy forces over long distances has declined in the last 30 years because of a lack of investment in large specialized roll-on roll-off ships. Many of the existing US reserve merchant marine ships dedicated to military use are overage and have been poorly maintained. Based on the deployment times achieved during Operation Desert Storm, it is estimated that within about three weeks the US could project two light infantry paratroop brigades into Israel by air, plus one Marine infantry brigade transferred by forward deployed USN amphibious ships and pre-loaded forward-based maritime ships. Given about nine weeks, the US would likely be able to field nine maneuver brigades in the Middle East consisting of three paratroop, three Marine, and three heavy armored brigades. Consequently, it would require about nine weeks for the US military to generate roughly 15% of the IDF’s ground force mobilizable order of battle. These US forces would only deploy about 10% of the number of armored fighting vehicles the IDF can field.

The USAF has a very limited number of combat aircraft currently deployed in Europe. With air-to-air refueling, it is estimated that these aircraft might be able to sustain the generation of about 90 sorties a day in support of Israel. But these few sorties, which only  14 I Israel Versus Anyone: A Military Net Assessment of the Middle East represent 5% of Israeli wartime capability, could only be generated if the host country where these aircraft are based were to allow them to be operated in support of Israel. In the past, this approval has not always been provided. Neither the USN nor USMC currently have any operational combat aircraft based on aircraft carriers or large amphibious ships that are normally deployed in the Mediterranean within range of Israel.

Via Adam K.

Claims about Gudrid Thorbjarnardóttir

Viking society wasn’t homogeneous. They had dealings with many different cultures and they lived in varied environments, from Danish and Swedish pasture to the sub-Arctic tundra of Norway and Iceland. In the early 11th century the best-travelled woman in the world must have been Gudrid Thorbjarnardóttir, whose remarkable journeys demonstrate the great distances the Vikings covered. She gave birth to a child in North America, met people of the First Nations and ate grapes in Vinland, made a pilgrimage to Rome and drank wine in Italy, and died as a nun in Iceland. Vikings lived in close contact with the Sámi people, whom they called Finns. In his earlier book, The Viking Way, Price pointed out that Norwegians and Swedes, at least, might be regarded as in some ways similar to the ‘circumpolar’ cultures which stretch from Greenland to Siberia, notably in what looks like shamanistic behaviour.

That is from Tom Shippey’s excellent LRB Vikings book review, interesting throughout.

No brain drain for Filipino nurses

We exploit changes in U.S. visa policies for nurses to measure brain drain versus gain. Combining data on all migrant departures and postsecondary institutions in the Philippines, we show that nursing enrollment and graduation increased substantially in response to greater U.S. demand for nurses. The supply of nursing programs expanded to accommodate this increase. Nurse quality, measured by licensure exam pass rates, declined. Despite this, for each nurse migrant, 10 additional nurses were licensed. New nurses switched from other degree types, but graduated at higher rates than they would have otherwise, thus increasing the human capital stock in the Philippines.

That is from a new paper by Paolo Abarcar and Caroline Theoharides, via Chris Blattman.

From the comments, on coronavirus and humidity

I am not convinced by the humidity hypothesis, as I don’t see it having much macro explanatory power globally, but I find the questions very important.  On New York City, I tend to blame all those cramped indoor spaces combined with bad ventilation systems, but that too is an unconfirmed hypothesis.  Anyway, here are the words of Daniel Hess:

Dear Tyler and Alex –

As you know the case fatality rate from COVID has been dropping dramatically from COVID. Many have suggested age profile and treatment advances are the cause urge you to consider indoor humidity as the biggest variable. It is *the* governing environmental variable for respiratory health, above all others and it is an accessible way for everyone to improve respiratory health. Urgently, CFR is likely to return in the fall and winter to its previously high levels unless this knowledge can be more widely disseminated.

The idea that the COVID death rate is dropping so rapidly primarily because of age or improvements in medicine does not explain why tropical and humid areas never had high death rates in the first place. Or why the CFR in the southeast was always lower than in the northeast, even before understanding of COVID improved.

Just look at these numbers (see table below) fresh from this morning from worldometers.info :

In Florida deaths/confirmed case is 0.015 but in New York it is 0.073. Is Florida medicine and age profile so much better than New York’s? Florida is a very old state and medicine is not regarded as more advanced in Florida than in New York. Both had to deal with COVID early and Florida’s age profile is particularly skewed old. In fact Florida is typically the retirement destination for aging New Yorkers.

In Mississippi deaths/confirmed case is 0.028 but in Massachusetts it is 0.072. Is Mississippi medicine and age profile so much better than Massachusetts’s? Mississippi is very poor and 40% black, and known to lag socioeconomically. Massachusetts is very wealthy and just 7% black, and known for its advanced medicine and socioeconomic success. If anything, you would expect a much higher CFR in Mississippi than in Massachusetts. But Massachusetts has cold winters, which translates into dry indoor air in the colder months.

In Georgia and Alabama, deaths/confirmed case are 0.019 and 0.017 respectively. In Michigan and Connecticut they are 0.069 and 0.088 respectively. Is Georgia so much younger and medically superior to Michigan? Is impoverished and 30% black Alabama so much younger and more medically advanced than wealthy Connecticut which is just 10% black? Of course not. You would expect Alabama to have a much higher CFR than Connecticut, but instead it is more than 5 times lower. This is an incredibly dramatic difference that is inexplicable until you realize that humidity (including indoor humidity) governs respiratory health to a very large extent.

It seems certain that seasonality plays a role, but more specifically indoor humidity. That is to say, where humidity seems to be most crucial is in reducing severity of symptoms and mortality for those already infected with COVID-19.

That was the finding of a group of 51 scientists in this new paper:

https://www.medrxiv.org/content/10.1101/2020.07.11.20147157v2.full.pdf

“Severity of COVID-19 in Europe decreased significantly between March and May and the seasonality of COVID-19 is the most likely explanation. Mucosal barrier and mucociliary clearance can significantly decrease viral load and disease progression, and their inactivation by low relative humidity of indoor air might significantly contribute to severity of the disease. ”

Innate respiratory immunity is impaired in conditions of low humidity, as has been shown extensively in this large review of the literature by a group led by renowned virologist Professor Akiko Iwasaki of Yale University. In fact, this may be the most comprehensive review of respiratory infection seasonality published anywhere:

https://www.annualreviews.org/doi/pdf/10.1146/annurev-virology-012420-022445

Folks, this is huge because it shows that a simple remedy (indoor humidification in temperate areas in winter months) can cut COVID-19 mortality by almost an order of magnitude.

Humidity as protection against respiratory infections is not new or surprising. Parents have been using humidifiers in nurseries for this reason for generations. Yet somehow, when it comes to COVID-19, all this knowledge is ignored. Madness!

Here is Alex’s source post, and there are a few interesting responses in the ensuing discussion.

Don’t mention the fake news

Even exposure to the ill-defined term “fake news” and claims about its prevalence can be harmful. In an experimental study among respondents from Mechanical Turk, Van Duyn, and Collier (2019) find that when people are exposed to tweets containing the term “fake news,” they become less able to discern real from fraudulent news stories. Similarly, Clayton et al. (2019) find that participants from Mechanical Turk who are exposed to a general warning about the prevalence of misleading information on social media then tend to rate headlines from both legitimate and untrustworthy news sources as less accurate, suggesting that the warning causes an indiscriminate form of skepticism.

That is from Brendah Nyhan’s good new JEP survey article on how misperceptions come about and persist.

Saturday assorted links

1. The polity that is Germany: “Light traps for insects are to be banned outdoors, while searchlights and sky spotlights would be outlawed from dusk to dawn for ten months of the year.’

2. The new Eisenhower  Memorial, by Frank Gehry, recommended, I am keen to see it.

3. Drive-in symphony concert.

4. Is the precautionary principle being applied to herd immunity claims?  And other interesting points on related matters.

5. Canadians taking revenge against visiting Americans (NYT).

6. Peptide antidotes, another promising treatment area.

7. Summary of the UK planning changes.

Bill Gates is Angry

But people aren’t getting their tests back quickly enough.

Well, that’s just stupidity. The majority of all US tests are completely garbage, wasted. If you don’t care how late the date is and you reimburse at the same level, of course they’re going to take every customer. Because they are making ridiculous money, and it’s mostly rich people that are getting access to that. You have to have the reimbursement system pay a little bit extra for 24 hours, pay the normal fee for 48 hours, and pay nothing [if it isn’t done by then]. And they will fix it overnight.

Gates is correct. If companies were paid for speed they would increase capacity and move immediately to a stack processing (LIFO) model, as I described yesterday.

The whole interview is worth reading. Gates is restrained but you can tell he is angry. Bill has had it with the FDA, Trump, Mark Zukerberg, stupid anti-vaxxers like Robert Kennedy (who he was forced to listen to to get access to Trump), Congress and much more. I don’t blame him one bit. I am angry too.