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استهداف عامل R وانتظار اللقاح

Apr 23, 2020 Ricardo Hausmann

كمبريدج- تعيش العديد من البلدان الآن حالة إغلاق بهدف الحد من معدل نمو حالات كوفيد- 19 والوفيات الناتجة عنه. ونظرا إلى التكاليف الباهظة لمثل هذه الجهود الرامية إلى "تسوية منحنى" عدوى كوفيد-19، فإن صناع السياسات يتعرضون لضغوط متزايدة من أجل "إعادة فتح الاقتصاد". ولكن كيف يمكنهم القيام بذلك بطريقة آمنة؟

بما أن الأعراض تظهر بعد مرور 5.2 يومًا في المتوسط على الإصابة بالعدوى، وتحدث الوفاة بعد 13 يومًا من ظهور الأعراض على المصاب، فمن المفترض أن ينخفض عدد الحالات الجديدة والوفيات إلى الصفر في غضون ثلاثة أسابيع، إذا كان الإغلاق سيؤدي إلى توقف الإصابات الجديدة. وبناءً على هذا المعيار، كانت الإجراءات الفعلية بطيئة إلى درجة تثير الذهول. فعلى سبيل المثال، فرضت إيطاليا إغلاقًا صارما في 9 مارس/أذار، وهو اليوم الذي سجلت فيه سلطات البلد 1797 حالة جديدة مؤكدة، و97 حالة وفاة جديدة. وفي 18 أبريل/نيسان، ارتفعت الأرقام إلى 3491 إصابة و482 حالة وفاة. ويموت الإيطاليون بمعدل أعلى أربع مرات مما كانوا عليه قبل الإغلاق.

ومع ذلك، يعتقد البعض، بما فيهم الرئيس الأمريكي دونالد ترامب، أن الوقت قد حان لتخفيف القيود. وإذا كان منحنى الوباء Uمعكوسًا بعد ذروته، فإننا قد تخطينا الأسوأ، أليس كذلك؟

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0 Comments on this paragraph, 12 Comments on this article

Ben Leet May 1, 2020

For the U.S. this is the rate of confirmed case expansion:
Between March 17 and April 1 —14 days — cases increase by a factor of 30
(from 7,023 to 213,144).
Between April 1 and April 15 — 14 days — cases increase by a factor of 3.
(from 231,144 to 632,548)
Between April 15 and April 29 -- 14 days -- cases increase by 55%, a factor of 1.55.
(from 632,548 to 981,246)
In the past week it was 1.29, so it is slowly moving toward R 1, or no case expansion. We plateaued at around 29,000 new cases between April 1 and April 24, and recently are going lower, around 24,000. But it will take a long time. I calculate that by Aug. 1 at this rate, 1.3, we will have 23 million cases, about 7% of population. And 230,000 deaths, 0.1% mortality rate. It is all so speculative. Recently a test of prison inmates indicated an infection rate of 70%, but it could easily be 100% by now, but 96% were asymptomatic cases, 4% with symptoms. We need a survey, a random widespread testing program, to determine how many are presently infected and asymptomatic. USC is also doing such random testing in the L.A. area, with similar results. The ultimate result is 330,000 deaths, which is superior to 2.2 million as Imperial College predicted in mid March, that was without mitigations such as social distancing. I write about Covid-19 at my blog, http://benL88.blogspot.com, maybe 100s of others use their spare time doing this research. I comment on R. Hausmann's articles on Venezuela often, I find them horrible, very caustic and unreasonable, supporting the worst accusations against the democratically elected government, without any balance admitting mistakes of the opposition, not recognizing the near majority support and voter turn-out for the present legitimate government. Venezuela has the highest homicide rate in the world, it's now suffering from commercial sanctions. It deserves reasonable compromise solutions, not fire and bullets. I find it very pleasant to find that he can present a decent case for ending this pandemic. Thank you, R.H., may your balanced appraisals be your new hallmark.
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Per Kurowski Apr 27, 2020

The absence of valid real time information about coronavirus / COVID19 deaths by the different age groups, is truly astonishing… and worrisome.

Is that information not of utmost importance in order to decide what to do?
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Dallas Weaver, Ph.D. Apr 26, 2020

That Ro number is socially determined by the product of frequency or number of interactions between people and the probability of transmission. As either of these can be reduced, in theory, to zero the Ro will become zero and the virus dies.
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Dallas Weaver, Ph.D. Apr 26, 2020

An excellent article putting the focus on Ro, where it should be.

It is useful to note that Ro depends upon the product of the "number of interactions" between people and the "probability of virus transfer" if one of the people is infected (if either goes to zero Ro goes to zero). The distancing and shutting down the economy approaches to decrease the interactions which decrease Ro while doing massive economic damage does little about the probability of transfer.

We know from health care workers, with massive numbers of interactions with known infected people, can reduce the transfer probability by a huge fraction with the proper use of personal protective equipment (PPE). This includes a face mask to protect against transfer by large exhaled particles from talking, sneezing, and coughing, along with disposable outer garments and shoe covers. This effectively makes a bubble around individuals so the physical distance becomes irrelevant. We know that hospitals have internal Ro of much less than one (if they didn't they would be the source of infections).

If a significant fraction of the population used a civilian version of PPE the Ro for the society would be less than one and this will go away. By making local businesses, manufacturers, logistical systems have Ro less than one we can open businesses.

However, we don't have enough disposable PPE for this option so the civilian PPE must be re-usable. This virus can easily be inactivated by simple heating to greater than 140ºF (60ºC) for 30 minutes which is the temperature of a dryer, food warmer, dry air sauna, or an oven or toaster oven. If the temperature is less than 220ºF (100ºC), masks, gloves, outer garments, and shoes are not damaged and can be reused.

As we allow more contacts between people we have to decrease the transfer probability by using PPE. For more details:
https://www.dropbox.com/s/lvmhxl4nyybprsi/Protection%20in%20the%20Covid-19%20era%20V4.pdf?dl=0
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Noora Mohammed Apr 25, 2020

This is very interesting and enlightening given the statistics included. A lockdown and a robust monitoring system could contain this virus sooner in order for economy to rejuvenate.
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Paul Daley Apr 24, 2020

Hausmann's advice is already out of date. Random testing in New York suggests that the number of cases is vastly greater than the confirmed cases published to date. The implication is that the effective R is much higher than earlier estimates might have suggested and that social distancing has failed dismally. So we may not have a tool that can be used to target R, or to slow the spread of the virus in high density environments. On the other hand, those same random statistics suggest that the virus is not nearly as lethal as had been feared. It can kill the vulnerable, but most others may never realize they have ever been affected. That suggests a strategy, pending development of a vaccine, focussed on isolating the most vulnerable until the virus passes through, and on treating those that do become sick. Anything more is likely to be simply a waste of money.
- Dallas Weaver, Ph.D. Apr 26, 2020
  
  You are making an assumption that the serological tests have a low false-positive rate and that you are not measuring a cross-reactivity. You are also assuming the antibodies being measured will provide immunity (lasting immunity to the common cold coronavirus has proved difficult).
  
  These assumptions may not be valid. Any attempts to let in burn through to obtain herd immunity before a vaccine may be very dangerous and result in an overloaded health care system and massive unnecessary deaths.
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NPH . Apr 23, 2020

"R-targeting until a vaccine arrives seems more sensible and humane, because it would both save lives and spare the economy."

I fear this is grossly overoptimistic. A vaccine will be a year at the earliest and possibly as late as 2022, if one can be developed at all. Coronaviruses are notoriously hard to develop a vaccine for; in fact, the FDA has never approved an effective vaccine for a coronavirus. The rush to reopen is rash and reckless, but believing it is sustainable or rational to stay in lockdown until a vaccine is ready is equally misguided. Doing so would not "spare the economy" but rather would condemn the economy to unprecedented catastrophe. Millions of small businesses would permanently close, and tens of millions families would be thrown into financial ruin and poverty after months of joblessness. Even just a month or so into this crisis, the government has already tacked on trillions to the debt in stimulus funding, and it is naive to think it is fiscally feasible for government stimulus to continue indefinitely.

Spanish flu (a relatively more lethal disease for what it's worth) was bad, but the Great Depression was worse. Any solution which causes a second Great Depression is no solution at all.
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Norman Kennedy Apr 23, 2020

This piece is very informative and very distressing. The economic damage may well be as harmful as the epidemic. I hope that the Ro for most areas was much higher than this piece suggests. I look forward to seeing if the R can be throttled with gradual lifting. I wonder about the actual date of Ro in Wuhan as to whether it was considerably earlier than late December 2019.
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Gerald Silverberg Apr 23, 2020

This article is still working with extremely sanguine estimates of R0. Many recent studies place it definitively above 3 and as high as 5.7.

See e.g. https://wwwnc.cdc.gov/eid/article/26/7/20-0282_article?deliveryName=USCDC_333-DM25287 and

https://www.nejm.org/doi/10.1056/NEJMoa2001316.

Nevertheless, effective public health measures ranging from classical test, trace and quarantine (Singapore, South Korea, Taiwan, Hong Kong) to drastic lockdown (China) have demonstrated that the disease can be contained or even eliminated domestically.

The real danger is preventing resurgences coming from abroad, a topic this article does not address. This would require the virus to be contained simultaneously worldwide, or very effective international quarantines to be maintained for long periods of time.
- Ricardo Hausmann Apr 23, 2020
  
  Rt depends on policy. I mention that before measures it was closer to 3. The question is how does it respond to different kinds of social distancing, test and trace and other policies. And of it does, is it feasible to contain it so that a significant part of the population is still susceptible by the time when we get the vaccine.
  - Gerald Silverberg Apr 23, 2020
    
    Rt, the effective reproduction number, indeed depends on policy and social behavior. But because the basic reproduction number R0 is so high, traditional public health measures do not seem adequate to control it, particularly in Western countries that learned nothing from SARS and Mers and allowed their cadre of tracers to decay. A recent study of the transmission dynamics indicates that only a digital app will permit tracing and isolation fast enough to suppress the disease without costly ongoing lockdowns, as has been achieved in East Asia: https://science.sciencemag.org/content/early/2020/04/09/science.abb6936.full.
    Lockdown fatigue is already being politically manipulated in the US to the point that the epidemic may resurge and become uncontrollable.
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استهداف عامل R وانتظار اللقاح

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