Heather MacDonald’s reasoning is not sound

Heather MacDonald writes,

Even assuming that coronavirus deaths in the United States increase by a factor of one thousand over the year, the resulting deaths would only outnumber annual traffic deaths by 2,200.

It is unsound to compare a relatively stable number (traffic deaths) to an exponential (the coronavirus). I hope that she will re-think and retract.

She writes as if increasing by a factor of 1000 is some sort of ridiculous upper bound. In fact, if we were to go ahead with business as usual and not do self-quarantining and social distancing, we would have to be darn lucky to have deaths increase only by a factor of 1000.

Lately, the number of cases in the U.S. and many European countries seems to be doubling every three days. If that pace continues, then in thirty days the number of cases will already be one thousand times what we have today. And in another two weeks, it would be 32,000 times the number of cases today.

Given this rate of spreading, one can expect that the number of deaths would double more rapidly than the number of cases. That is because the health care system would be overwhelmed. There would be too many critically ill patients to be able to treat them all.

As of Friday afternoon, there were about 2000 cases in the U.S. If 1000x were the upper bound for the spread of the virus, then we would see 2 million cases. If I thought that Americans could go about our normal business and have no more than 2 million cases, I would advocate going about our normal business. But instead, even with the actions that we have taken to date (note that these are less drastic than actions taken in several other countries), I think that holding the number of cases to 2 million would be optimistic.

I hope that I turn out to be foolishly alarmed about the way that this virus spreads. But to me, the exponential looks formidable.

Meanwhile, Tyler Cowen points to the British policy. As far as I can tell, they seem to be saying that you only need to worry about isolating known cases.

Some critics believe that the British approach will not slow the spread of the virus, and that the Brits know this. These critics see the Brits as consciously preferring to expose a large share of their population soon, on the theory that once they have immunity the crisis will be behind them.

The potential downside of that approach is that they might soon see their medical facilities overwhelmed, so that more cases become severe and fatal than otherwise might be the case. But if not, and their approach works, then they can certainly laugh at the rest of us.

Also, perhaps by the time you read this the Brits will have re-thought and retracted.

21 thoughts on “Heather MacDonald’s reasoning is not sound

  1. The upper bound in the US is around 300M cases (ie nearly everyone) and something like 3M – 10M deaths. The death rate is unclear and anyway the virus will mutate into different forms.

    The maths is pretty simple but most people can’t grasp simple maths. Linear is how we are naturally wired. Non-linear needs some maths education.

    China has demonstrated it is possible to control the spread. Their daily new cases are below 1% of the global total (yesterday was <0.2%), with the majority of existing cases and 20% of the world population.

    • It is certainly possible to control the spread of almost any disease, if you are able and willing to do what the Chinese have done. They aren’t just slowing the pace of new infections so the medical system can cope, they are trying to prevent most of the county from ever getting infected, by impressive, heroic efforts.

      The trouble is, they can’t keep it up forever. And if they relax before everyone gets vaccinated (which could be a while), before the world is through with the wave, and don’t keep the borders nearly air tight, then because they won’t have herd immunity, all those people who never got infected could kick off another round of outbreak, maybe even worse (seems to be a possibility contemplated by the UK management strategy theory).

      It is slightly good that the world is running a series of varying experiments and we might be able to learn something new about this kind of thing. In just a few months, we’ll know a lot more about what worked and what didn’t, at unfortunately catastrophically terrible cost.

      • It seems quite possible that an immunoassay for the Wuhan virus will be developed soon. Those give results in ~10min rather than ~10hr. They can then just test everybody coming in – include cost in airport fees if necessary. Combined with sufficiently aggressive local reporting, testing and contact tracing of confirmed positive cases, they might well be able keep going as is until a vaccine suitable for mass vaccination is available. If it turns out to be impossible to produce a vaccine, they can always shoot for herd immunity later.

    • As the fraction of people who’ve had it goes up, the rate of spread will decline dramatically, especially once a large fraction have had it. In the long run, yes, the trend is everyone will get it, but if we’re talking about this season – or even this year – I think nearly everyone getting it is almost impossible. Also, you’re assuming a lower bound mortality rate of 1%, which I would say is more of an upper bound.

      Mac Donald’s assumption of ~10-20% upper bound is of course unrealistic, since the flu infects 8% of people every year even with vaccines, covid-19 seems somewhat more contagious. With a “let it burn” approach, we would probably expect at least a few times as many people to get this as the flu in a given season right now.

  2. …the British policy. As far as I can tell, they seem to be saying that you only need to worry about isolating known cases.

    I think it is fairer to say that they are focused on immediate self-isolation within hours of your first symptoms. It’s also cynical and possibly entering conspiracy theory territory to claim that the strategy is to secretly move the population from fully Susceptible to fully Recovered in an SIR model. They clearly stated that 80% of the population is the upper limit and the death rate is 1%; 536K deaths in the U.K. is unthinkable as is 2.6M in the U.S. and those would be independent of the secondary deaths due to the crashed health system.

    We are highly infectious with the onset of mild symptoms and for the first four days afterwards. That nagging cough is potentially deadly. That is the message we should focus on.

  3. I think the Brits are right. Build herd immunity to what is, after all, only a really bad cold virus. To which children are immune by the way, and the vast majority of middling healthy non-elderly adults.

    And jeez, what suddenly happened to all of America’s “libertarians”?

    I think we need a federal program to buy adult diapers for all libertarians.

    The worst news out there is that the House has thwarted President Trump’s plan for a payroll-tax holiday (FICA) through the end of the year. And the Federal Reserve is armed with popguns.

    So let us promote hysteria, destroy several industries, crush Wall Street, and perhaps in the end collapse our financial system again. And throw a lot of people out of work.

    • Control of contagious disease is a traditional activity of classical-liberal governments, even if it involves buying adult diapers. I have even seen complaints that such governments treated contagious disease as more important than malnutrition.

  4. .. and, 1 month ago Italy had 3 cases confirmed. Two week ago, 1,100 cases. Today it has 17,600 with 2,500 new in one day.

    Spain had 2 cases confirmed one month ago, 45 cases two weeks ago. Today it has 4,200 with 1,300 new in one day.

    Picture no serious action.. Italy and Spain with 300,000 new cases each day two weeks from now. It might seem quite important to change to serious action then.

  5. The Brits approach is basically: “We don’t care about our elderly and/or we don’t understand that the incubation period is an average of 5 days without symptoms, at least some of which is highly contagious.” I don’t know how anyone could look at Italy or Spain and do what they’re doing. Or even what we are doing.

    It also drives me crazy when people try to compare this to the flu. People get flu shots, which is why people don’t panic over the flu. No one is vaccinated for this one, and it’s incredibly contagious.

    By the way, this is the essential twitter follow right now:
    John Burn-Murdoch’s daily update of case trends ~33% per day in Western countries. Keep in mind: log scale y-axis. You can see the difference policy makes between and within countries to some degree.

    • The Brits understand that the incubation is 5 days and non-contagious during this period. There are no asymptomatic super-spreaders. Italy, Spain, and the U.S. fit the model of community spread by people ignoring the need to self-isolate when symptoms appear.

      Let’s be charitable. The policy rests on the assumption that people are infectious for four days when symptoms first appear and that infection spreads via cough droplets. Given those assumptions, backed by strong evidence, the policy seems to be a simple and timely heuristic that will save the greatest number of lives including the most vulnerable.

      • RAD,

        There is high uncertainty on this.

        The incubation range is large, the median is around 3-4 days with a wide distribution (histogram of incubation period from Wuhan cases from a peer reviewed paper shows a frequency distribution from 1-21 days with a peak at 3 days). Can someone without apparent symptoms transmit? Uncertain, perhaps.

        Go to scholar.google.com, put in Coronavirus and select papers written in 2020. You’ll find peer reviewed papers.

        • I don’t think there is high uncertainty in this anymore. We have a range from very large but incomplete datasets in most jurisdictions to small but nearly complete datasets in a handful of jurisdictions. Complete datasets include Contact Tracing efforts hopefully coupled with objective biometrics such as body temperature and definitive tests for presence of the virus.

          If you don’t trust these assumptions then self-quarantine (asymptomatic isolation) is the best option.

        • There is high uncertainty. A big reduction in uncertainty soon would enormously beneficial.

          Handle Proposal #4: “Test The Prisoners.”

          Alas, because we are humane and enlightened we would never succumb to the temptations generated by a mere global emergency and allow prisoners to volunteer en masse for clinical trials and observations of progression of symptoms and contagiousness, in win-win exchange for clemency and commutation of their sentences, so we could know all those things very well and very, very fast.

          Just because that kind of quick and quality actionable intelligence about the contagion is a public good worth literally trillions of dollars to everyone, including prisoners, shouldn’t let us lose sight of our more fashionable values and need to show off how righteous we are.

  6. If 20% of people get the virus this year – a number I think both optimists and pessimists would agree is a reasonable possibility – that would probably entail a solid 300k deaths and possibly 500k or so, depending on how overwhelmed the healthcare system is. We would officially have a new 3rd place cause of death after cancer and heart disease. If 30-40% get it this year – which can’ yet t be ruled out as an absurd scenario – it could kill more people than heart disease (647k).

    Putting it that way, pending new evidence, it is impossible to deny that there is a reasonable possibility that coronavirus will be the leading cause of death in the US this year; that’s pretty hard to reconcile with a ‘do nothing’ approach. Unless you chain smoke, chew tobacco, and never try to eat healthy or exercise, in that case you may be risk-tolerant enough that this is the rational approach.

    • Unless you chain smoke, chew tobacco, and never try to eat healthy or exercise, in that case you may be risk-tolerant enough

      Actually I understand that the virus is exceptionally hard on ex-smokers and early data is showing ex-smokers have a higher chance of death that current smokers. Considering the data is still limited here a self-selection bias of ex-smokers are older, avg. age 60, than smokers, avg. age 30. But smoking does a lot to compromise your lungs for rest of your life.

  7. Have any jurisdictions experimented with age-based quarantines? Rather than shutting down everything, it seems like it would be pretty straightforward to limit access to public gatherings to people who are under the age of 40 or 50 or 60. It should be pretty straightforward to identify most people who look like like they are too old to be out during the quarantine period and request identification accompanied with the threat of a fine. How long such a policy would need to be in place in order to manage the spread of the virus to preserve the capacity of the health care system?

  8. The UK has directed people over 70 to stay home for the next four months.
    My impression is that the people in charge in the UK are smarter and more on top of things than their counterparts in the US. When the post-mortems are done it will be interesting to see the analysis of the costs and benefits of closing all the schools.

    • People over 70 are the ones who are mostly likely to need assistance, even in the absence of the coronavirus. Eventually, they will need food, medication refills, help with other medical problems. Seems like wishful thinking that they can just stay at home for a prolonged period of time. But I guess the theory here is that they will develop herd immunity quickly instead of trying to prolong the disease outbreak. Will certainly be interesting to see how it plays out.

      The scary thing about this is how varied the outcomes are. Many people seem to be asymptomatic or have very mild symptoms, and for others it is life threatening. And I’ve heard reports are some people who have the mild symptoms for several weeks (can’t find any links at the moment on this, so maybe take it with a grain of salt… I had seen that one of those infected on a cruise had been positive for several weeks). Also, SARS and MERS caused permanent lung damage in some survivors, and it’s not clear what the long term effects of this one are. I’m guessing in the mild cases, there won’t be many problems, but I’d also guess for many of the ~20% of cases that are not fatal but serious that there may be long term issues even after recovery.

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