How many people have been exposed to Covid-19 ?

In the last few days, there have been quite a few reports of studies suggesting that the number of people who have been exposed to Covid-19 is far larger than previously thought. These studies have been based on testing for antibodies against coronavirus (it is unclear whether they are specific to Covid-19, or might reflect exposure to other coronaviruses).

I’m finding it difficult to square these estimates with inferences from direct testing, which (as I understand it) tests whether people currently have the disease. This is a point on which I would really like to see a clear explanation from an epidemiologist, but I haven’t seen one, so I am going to set out my own thoughts.

Alert: Unlike my discussion of the exponential growth rate R, where I was confident in the analysis and rapidly proved correct, this is an amateur effort and I could easily be missing something crucial

Suppose that

  • the virus has been around for some number of days D
  • infected people will give a positive response to a direct test for d days
  • the proportion of positive test results in a random sample of the population is p

Then, as a first approximation, the proportion of people ever exposed is (D/d)p. To estimate D, I’ll assume that very few* people outside China were infected before 1 February, which gives D = 84 as of April 25. I’m less clear about d, but 14 days appears to be the standard estimate for asymptomatic cases. That gives D/d = 6.

The big problem is p. Most places are only testing people who are at high risk because of symptoms or known contacts. Iceland gave 1800 tests to randomly selected volunteers in March, and got a positive rate of 1 per cent, suggesting that the proportion ever exposed would be 6 per cent. That’s a lot of people, but nowhere near enough to make herd immunity a relevant possibility.

Any ideas?

  • Some were, it’s clear, but if the numbers had been large, we would have seen many more deaths.

No planet but this one

The Voyager 2 spacecraft has just passed through the heliopause and into interstellar space, forty years after it was launched.

On the one hand that’s a stunning technological achievement and a reminder of the wonderful universe we live in. On the other, it’s a reminder that humans will never go out to explore this universe, or even leave Earth in significant numbers.

Although Voyager 2 has passed the heliopause it is still within the gravitational field of the sun. It would take another 30,000 years to fly beyond the Oort cloud which marks the boundary.

These facts could have been computed when Voyager was launched though at the time its mission was limited to five years. But if they had been pointed out as an argument for the impossibility of interstellar travel, the response would surely have been that the problem would be solved by technological progress. Forty years before Voyager was launched, flying across the Atlantic ocean was a major feat. Forty years or so before that, the first heavier-than-air flight was undertaken by the Wright brothers.

Extrapolating one could reasonably expect that forty years more progress would produce massive advances in space travel including human space travel. In fact, though no one knew it at the time, the heroic age had already passed. No one has travelled to the moon since Voyager 2 was launched and, quite possibly, no one ever will. The promise of the space shuttle has been abandoned in favour of the 1950s technology of the Atlas rocket. Meanwhile physicists have closed off just about every possible loophole that might allow us to evade Einstein’s conclusion that the speed of light is an absolute limit.

The other achievement of the Voyagers and their successors has been a comprehensive exploration of the planets and moons of the solar system. They have revealed many marvels, but nowhere remotely habitable compared to, say, Antarctica or the Atacama desert.

The biggest lesson of our decades of space exploration is that Earth is the only planet we have.

The Coal Truth

Last week, I spoke at a forum on Adani and indigenous rights organized by the UQ Human Rights Consortium. It was an excellent line-up, with

Murrawah Johnson – Youth Spokesperson Wangan and Jagalingou Traditional Owners Council, Activist of the Year (Ngara Institute) and on the 50 Grist list – acknowledging her place amongst the world’s best and brightest fighting for the planet.

Dr Michelle Maloney – Co-founder and National Convenor, Australian Earth Laws Alliance

David Ritter – Chief Executive Greenpeace Australia Pacific, and author of The Coal Truth: The Fight to Stop Adani, Defeat the Big Polluters and Reclaim Our Democracy which is well worth buying and reading.

Having contributed to The Coal Truth I was very interested to meet David Ritter. I was particularly impressed that he took the time to respond personally to this long-ago post, attacking Greenpeace for the sabotage of a CSIRO experiment on GM crops. David assured me that Greenpeace had repudiated this action and re-established a good relationship with CSIRO.  There’s plenty of room for legitimate dispute about the issue of GM crops (I’m dubious, thought not opposed outright) but none about the kind of tactics used in that case.

An unhappy coincidence?

The other day my incoming email included an invitation from an Olla Galal, special issue developer at Hindawi publishers, to be the Lead Guest Editor for a Special Issue of Occupational Therapy International. Nothing too surprising in that, although my knowledge of occupational therapy would barely extend to a paraphrase of the name. I’m always getting invitations like this, and while I had the impression that Hindawi was a cut above the kind of predatory publishing house that does this kind of thing, I wasn’t too sure. (I have received previous invitations of this kind from them, but in fields where I could at least be a plausible candidate.

What made me pay attention was this

In June 2016, Wiley and Hindawi entered into a new publishing partnership that converted nine Wiley subscription journals into Open Access titles. The journals will be published under both the Wiley and Hindawi brands and distributed through Hindawi’s online platform

So, if this is accurate, I could become a guest editor for a Wiley journal in a field in which I am totally unqualified. More seriously, authors of papers in the old version of Occupational Therapy International “very well respected in its field with an impact factor of 0.683” according to Olla Galal, will now be associated with the new one.

Having got this far, I thought I should check Beall’s list of predatory journals, only to discover that it went dark on 17 January* for unexplained reasons. This is certainly depressing. It seems that even supposedly reputable academic publishers are now engaged, with only the fig leaf of a “partnership”, in seriously predatory behavior. How long before we see them pandering to the demand for “alternative fact” journals to give proper credibility to creationism, climate science denial, antivax and so on, if they are not already?

* Only a couple of days before Trump’s inauguration. Coincidence?

My letter to Paul Offit (updated)

Dear Dr Offit,

I have admired your work in support of vaccines, and your willingness to face down the anti-science attacks on vaccination. I was, therefore, greatly dismayed to read your column in the Daily Beast recently, reviving a set of discredited attacks on public health and environmental science, centred on the spurious claim of a global ban on DDT. I have linked a blog post and article covering the key points, which you can easily check for yourself

As I note in the post, giving credence to discredited anti-science attacks like those of Stephen Milloy is a gift to the anti-vaccination movement which they are already exploiting. I urge you to investigate this issue more carefully and publish a follow-up column setting out the real situation.

I would be happy to correspond further and send you more information if needed.

John Quiggin

Update 21/2/17: I received a fairly terse reply to this email, reiterating a number of spurious claims about Carson. My email in response went unanswered, as did a followup. This is disappointing, but if there’s one thing I’ve learned in 15 years of blogging it’s that changing anybody’s mind is very difficult. I’ve done my best to apply this lesson to myself and be more open to new evidence – long term readers can judge if that’s been successful.

A double disaster for science and public health

Zombies never die, and that’s even more true of zombie ideas. One of the most thoroughly killed zombies, the myth that Rachel Carson is responsible for millions of deaths from DDT, has recently re-emerged from the rightwing nethersphere where it has continued to circulate despite repeated refutation. That wouldn’t be worth yet another long post except for the source: Dr Paul Offit, a prominent pediatrician and leading pro-vaccination campaigner, writing in the Daily Beast. Offit’s revival of the DDT ban myth is a double disaster for science and public health.

Read More »

Tu quoque, revisited

Slightly lost amid the furore over the alleged Trump dossier was the news that Trump had held a meeting with leading antivaxer Robert F. Kennedy Jr. As is usual, particularly with the Trump Administration, accounts of the meeting differed, with RFK claiming Trump had asked him to lead an inquiry into vaccine safety and Trump apparatchiks denying any firm decision had been made.

This interested me because, on the strength of sharing his father’s name, RFK Jr was, for many years the poster child for those on the right who wanted to claim that Democrats were just as anti-science as Republicans. (I’ve appended a post from 2014, discussing this.) Now he’s eager to work for Trump.

I pointed out the likely emergence of vaccination as a partisan issue in another post. Lots of commenters were unhappy about it, and it’s true that it’s unfortunate in the same way as is the partisan divide on global warming, evolution and just about any scientific issue that has political or cultural implications. But, whether we like it or not, it’s happening and likely to accelerate. The sudden reversal in Republican views on Putin, Wikileaks and so on illustrates the force of loyalty to Trump. We can only hope that, for once, his team’s denials turn out to be correct.

Read More »

Catalyst catastrophe

There are reports that the ABC’s Catalyst science program is to be dumped, and replaced by a series of specially commissioned 1-hour documentaries. The move has reportedly been prompted by the disastrous broadcasts of Maryann Demasi, on the supposed dangers of statins and wifi. I have mixed feelings about this. Catalyst has serious problems, going beyond Demasi, but the alternative sounds like it will require a lot of money to do well. I fear that “specially commissioned” will turn out to mean “recycled from Discovery Channel” and that we will end up with lots of variants on “Shark week”

More generally, it’s depressing to reflect on the near-total failure of television as a communications medium for science. The demands of the medium (flashy visuals, and continuous sound) overwhelm what ought to be its potential. Discovery Channel is a joke that makes Catalyst at its worst look good. Even the great David Attenborough is now presented inaudibly, drowned out by the monotone background noise of Sigur Ros. Overall, radio is better, and text better still.

A question about group selection

I’m doing some work on evolutionary models of game theory and need to understand the debate about group selection. It seems pretty clear that the great majority of evolutionary biologists reject the idea of group selection, but I haven’t found an adequate (to me) explanation of why they do so. A crucial problem for me is that the literature seems, without exception as far as I can see, to conflate group selection with co-operation and altruism. But the problem of group selection arises in non-cooperative settings, provided they are not zero-sum.

To illustrate the problem I’m struggling with, suppose that two previously isolated species meet as a result of some change. In one species (peacocks), competition between males for mates takes the form of elaborate, and energetically costly, displays. In the other species (penguins) males compete by providing food to their mates. In all other respects (diet, predators and so on) the two are similar. It seems obvious to me that the penguins, with their more efficient social arrangements, are going to outbreed the peacocks and eventually drive them to extinction.

It seems to me there are only two possibilities here
(a) My reasoning is wrong, and we can’t judge which species, if either, will dominate; or
(b) Even though it involves one group being selected over another, this isn’t what is meant by group selection

I’d really appreciate some help on this. I’m happy to have thoughts from anyone, but I’d most like to hear from actual experts with contact details.

Public funding for phlogiston ?

According to the Oz, Queensland LNP Senator Matt Canavan has called for public funding for research promoting his belief that scientists since Arrhenius have been wrong about climate change. He makes this claim on the basis that the overwhelming body of evidence amassed by mainstream science means that “only one side of the debate is heard” (there’s also something about witches). Oddly enough, Canavan goes on to cite some (presumably publicly funded) research on aerosols from the Max Planck Institute which he thinks supports his arguments. The fact that such research gets undertaken and published suggests that there is no problem with the scientific process as regards climate change.

Still, there’s an interesting question here. To what extent should research funding seek to promote research approaches that are regarded by most experts in the relevant field as wrong or discredited?

In fields like economics, the ebb and flow of opinion is such that any temporary appearance of consensus is illusory. When I started studying economics, the dominant Keynesian/market failure school regarded classical economics as a collection of exploded fallacies. Within a decade or so, the position had reversed. Free market microeconomics and New Classical microeconomics became dominant and remained so until the Global Financial Crisis. The position now is best described as confused. Something similar could be said of fields like psychology (another example where plenty of non-specialists have strongly held views)

In the natural sciences, there are a lot more firmly established conclusions, which nonetheless run against the prejudices of many (obviously including Senator Canavan). I don’t see any merit in funding the pet theories and tribal prejudices of politicians. But at the frontiers, there are lots of instances where some particular approach (such as string theory in particle physics) seem to be dominant, at least in part, for sociological reasons. Here it would be desirable to ensure that alternative approaches get a hearing.

Any thoughts?