3 ms·

"growth rate matters vastly more" Only in the case where you deny the existence of uncertainty in that number. Also, it's generally considered that infectious

"growth rate matters vastly more" Only in the case where you deny the existence of uncertainty in that number. Also, it's generally considered that infectious and lethal diseases rapidly evolve to become less virulent, since the people that are sickest tend to be more isolated.

dredmorbius 7y ago
No. The point is that initial quantity has virtualy no impact on final result, as compared with growth rate. With a doubling time of under two days, a misestimation by a factor of two ... is resolved in a day. By a factor of 10, in about 3 days. By a factor of 100, in six. By a factor of 1,000, in 12. It's not uncertainty about the growth rate, but change which matters, and which epidemiological containment is concerned with. The goal is to change the transmission rate (R factor), and through that, the rate of growth of the epidemic. Epidemics of the past which have proved highly lethal (look through your favourite list of historical plagues) have killed from 10% to half of local populations, often through a combination of high mortality but slow onset. Spreading before* symptoms are clearly expressed will suffice. The Black Death spread throughout Europe from 1346 - 1353, over eight years, killing up to 60% of the population. It returned multiple times, through 1667, with recurrence mortalities of 10-20%. It continued through the 19th century in the Arabic world. Expecting a novel virus to attenuate markedly in a few days or weeks seems wishful thinking.
- perl4ever 7y ago
  "It's not uncertainty about the growth rate, but change which matters" You're saying growth rate is not rate of change and the rate of change is important, but the difference between two different rates of change is insignificant? My point was that the R factor is neither constant nor precisely known, whatever people do. If the outcome is very sensitive to the number, then it seems to me obvious that it is very important to look at the outcome over the range of possibilities, because it's going to be a large range. Whenever professionals make long term predictions, they usually depict them as a cone. How big it is and how it widens is important. Also, I thought the plague was bacterial, so I'm doubtful of the inference that a virus won't evolve rapidly. Previous flu epidemics did, right?
  - dredmorbius 7y ago
    I'm sorry, but I appear to be having difficulty in expressing myself clearly. Growth rate is obviously a rate of change. Specifically: of growth. The growth rate of an epidemic, disease, population, or any other phenomenon, is not a constant over all time. It can however be assessed at any given point in time. And frequently remains largely similar for period of time. Which is to say: the rate of change is itself subject to change. By analogy, speed is a rate of change, but speed itself can be subject to change through acceleration. You seem to be arguing (though I'm understanding your argument poorly as well) that growth rate doesn't matter. You've not indicated what it is that you do think matters. My argument is that of the two measures, initial population and growth rate, the first matters little, and the second effectively entirely defines observed behaviour, that is, growth. I am not arguing, though you seem to understand I am, that the growth rate will be constant for all time. The growth rate will change. That is the entire purpose of epidemiological intervention. I AM arguing that the change in the growth rate is everything that matters about the 2019-2020 Wuhan Coronavirus Outbreak, and its eventual resolution. Any uncertainty about the growth rate still affects the rate of growth, and to that extent, is material. Uncertainty does not change the fact that rate of growth entirely determines the course of the epidemic. I do hope that's clear.
    - dredmorbius 7y ago
      s/specifically of growth/specifically of population or count/

dredmorbius 7y ago

No. The point is that initial quantity has virtualy no impact on final result, as compared with growth rate. With a doubling time of under two days, a misestimation by a factor of two ... is resolved in a day. By a factor of 10, in about 3 days. By a factor of 100, in six. By a factor of 1,000, in 12. It's not uncertainty about the growth rate, but change which matters, and which epidemiological containment is concerned with. The goal is to change the transmission rate (R factor), and through that, the rate of growth of the epidemic. Epidemics of the past which have proved highly lethal (look through your favourite list of historical plagues) have killed from 10% to half of local populations, often through a combination of high mortality but slow onset. Spreading before* symptoms are clearly expressed will suffice. The Black Death spread throughout Europe from 1346 - 1353, over eight years, killing up to 60% of the population. It returned multiple times, through 1667, with recurrence mortalities of 10-20%. It continued through the 19th century in the Arabic world. Expecting a novel virus to attenuate markedly in a few days or weeks seems wishful thinking.

perl4ever 7y ago
"It's not uncertainty about the growth rate, but change which matters" You're saying growth rate is not rate of change and the rate of change is important, but the difference between two different rates of change is insignificant? My point was that the R factor is neither constant nor precisely known, whatever people do. If the outcome is very sensitive to the number, then it seems to me obvious that it is very important to look at the outcome over the range of possibilities, because it's going to be a large range. Whenever professionals make long term predictions, they usually depict them as a cone. How big it is and how it widens is important. Also, I thought the plague was bacterial, so I'm doubtful of the inference that a virus won't evolve rapidly. Previous flu epidemics did, right?
- dredmorbius 7y ago
  I'm sorry, but I appear to be having difficulty in expressing myself clearly. Growth rate is obviously a rate of change. Specifically: of growth. The growth rate of an epidemic, disease, population, or any other phenomenon, is not a constant over all time. It can however be assessed at any given point in time. And frequently remains largely similar for period of time. Which is to say: the rate of change is itself subject to change. By analogy, speed is a rate of change, but speed itself can be subject to change through acceleration. You seem to be arguing (though I'm understanding your argument poorly as well) that growth rate doesn't matter. You've not indicated what it is that you do think matters. My argument is that of the two measures, initial population and growth rate, the first matters little, and the second effectively entirely defines observed behaviour, that is, growth. I am not arguing, though you seem to understand I am, that the growth rate will be constant for all time. The growth rate will change. That is the entire purpose of epidemiological intervention. I AM arguing that the change in the growth rate is everything that matters about the 2019-2020 Wuhan Coronavirus Outbreak, and its eventual resolution. Any uncertainty about the growth rate still affects the rate of growth, and to that extent, is material. Uncertainty does not change the fact that rate of growth entirely determines the course of the epidemic. I do hope that's clear.
  - dredmorbius 7y ago
    s/specifically of growth/specifically of population or count/