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There has been a clear divergence, even accounting for the expected lag in death rate. The daily case count and daily death count initially look like two of th

by zaroth 6y ago

There has been a clear divergence, even accounting for the expected lag in death rate. The daily case count and daily death count initially look like two of the same curve simply shifted — as you might expect. Since approximately mid-April that has no longer the case and they are fundamentally different curves. You can see it here if you scroll down to where the daily charts are one above the other; https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html https://www.nytimes.com/interactive/2020/us/coronavirus-us-c... Something big changed (or several smaller somethings) mid-April to cause this divergence. If the case count measurement is no longer measuring actual positive cases, that could be a big part of the problem.

starkd 6y ago
That could be because the newer cases are younger people, and the mortality rate is much lower. There are many people who get it who are completely asymptomatic.
slg 6y ago
Testing has been on a rather steady increase and was truly awful in April. I know multiple people who had mild symptoms and couldn't get tested in April. We simply can't assume those case numbers from April are anywhere close to accurate. In all likelihood we had a huge case spike in April and we just don't have the test results to prove it. The April peak in new cases is therefore dampened to make it look like we had 3 months of roughly similar new case numbers when in actuality we had 3 months of declining cases. This is generally backed up by the percentage of positive tests[1] which saw a huge drop from April to the beginning of June before starting to increase again in late June. That spike isn't far enough in the past for the lagging death total to start increasing yet. Odds are the daily death increase is right around the corner. TL;DR - The new cases plot is not predictive of the new death plot because cases are a function of new tests while deaths happen regardless of testing. [1] - https://coronavirus.jhu.edu/testing/individual-states https://coronavirus.jhu.edu/testing/individual-states
- zaroth 6y ago
  I understand what you are describing and generally agree with it, except perhaps for your ultimately prediction. The death rate may ultimately increase, but it would not be simply because the current population of non-recovered cases haven't run their course. The total case count in theory is a factor of test capacity * positivity rate (ignoring distortions from "probable" cases). Death count also theoretically requires a positive test, so that curve could similarly be impacted by limited testing, but certainly the death part is getting measured in any case. The positivity rate itself can be impacted by limiting testing criteria based on symptoms (but, e.g. perhaps not if you were limiting based on just demographics). Presuming we were heavily test constrained in March/April, and were limiting testing based on symptoms, so you would have an increase in positivity rate but a lower test count. COVID death count could be low depending on how limited testing was for autopsy purposes, and whether deaths could be ruled being as due to COVID without a positive test. As testing capacity increases, and testing criteria is loosened, you would expect a lower positivity rate (for the same actual community disease burden) and a greater percentage of actual COVID deaths to be correctly diagnosed (perhaps a lower number of mis-attributed COVID deaths)... there's too many variables here to say for sure, but I would still expect the curves to have the same shape, even if the IFR ultimately goes down because you are catching more cases. The curves are clearly going in different directions. At first I attributed the divergence to new cases being limited to a younger demographic. If case count is increasing, but it is infecting a demographic with an order of magnitude lower IFR, then death count still decreases over time. But I'm beginning to think this doesn't fully explain it. There are clearly multiple forces at play, and the situation resists simplistic explanations. And all that is even ignoring the changes in medical protocols, like avoiding ventilators, and more recently, administering dexamethasone. Anecdotally, the majority of cases today come in as a young adult with mild symptoms (someone who probably wouldn't have even been tested in April, let alone admitted), they get a course of dex and antibiotics, are monitored for a couple days, and sent home. I think if the current active cases were to largely resolve without spreading, or if they spread mainly within their current demographic, then we will not see a major spike in COVID deaths. If the current surge in young adult infections ultimately results in a second wave of elderly infections then it's a different story. But I don't see an inevitable surge in deaths due to the current case count spike. And to the extent that the surge in cases are "probable" and not even confirmed, we could be looking at a lot of smoke without any fire.

by zaroth 6y ago

starkd 6y ago

That could be because the newer cases are younger people, and the mortality rate is much lower. There are many people who get it who are completely asymptomatic.

slg 6y ago

Testing has been on a rather steady increase and was truly awful in April. I know multiple people who had mild symptoms and couldn't get tested in April. We simply can't assume those case numbers from April are anywhere close to accurate. In all likelihood we had a huge case spike in April and we just don't have the test results to prove it. The April peak in new cases is therefore dampened to make it look like we had 3 months of roughly similar new case numbers when in actuality we had 3 months of declining cases. This is generally backed up by the percentage of positive tests[1] which saw a huge drop from April to the beginning of June before starting to increase again in late June. That spike isn't far enough in the past for the lagging death total to start increasing yet. Odds are the daily death increase is right around the corner. TL;DR - The new cases plot is not predictive of the new death plot because cases are a function of new tests while deaths happen regardless of testing. [1] - https://coronavirus.jhu.edu/testing/individual-states https://coronavirus.jhu.edu/testing/individual-states

zaroth 6y ago
I understand what you are describing and generally agree with it, except perhaps for your ultimately prediction. The death rate may ultimately increase, but it would not be simply because the current population of non-recovered cases haven't run their course. The total case count in theory is a factor of test capacity * positivity rate (ignoring distortions from "probable" cases). Death count also theoretically requires a positive test, so that curve could similarly be impacted by limited testing, but certainly the death part is getting measured in any case. The positivity rate itself can be impacted by limiting testing criteria based on symptoms (but, e.g. perhaps not if you were limiting based on just demographics). Presuming we were heavily test constrained in March/April, and were limiting testing based on symptoms, so you would have an increase in positivity rate but a lower test count. COVID death count could be low depending on how limited testing was for autopsy purposes, and whether deaths could be ruled being as due to COVID without a positive test. As testing capacity increases, and testing criteria is loosened, you would expect a lower positivity rate (for the same actual community disease burden) and a greater percentage of actual COVID deaths to be correctly diagnosed (perhaps a lower number of mis-attributed COVID deaths)... there's too many variables here to say for sure, but I would still expect the curves to have the same shape, even if the IFR ultimately goes down because you are catching more cases. The curves are clearly going in different directions. At first I attributed the divergence to new cases being limited to a younger demographic. If case count is increasing, but it is infecting a demographic with an order of magnitude lower IFR, then death count still decreases over time. But I'm beginning to think this doesn't fully explain it. There are clearly multiple forces at play, and the situation resists simplistic explanations. And all that is even ignoring the changes in medical protocols, like avoiding ventilators, and more recently, administering dexamethasone. Anecdotally, the majority of cases today come in as a young adult with mild symptoms (someone who probably wouldn't have even been tested in April, let alone admitted), they get a course of dex and antibiotics, are monitored for a couple days, and sent home. I think if the current active cases were to largely resolve without spreading, or if they spread mainly within their current demographic, then we will not see a major spike in COVID deaths. If the current surge in young adult infections ultimately results in a second wave of elderly infections then it's a different story. But I don't see an inevitable surge in deaths due to the current case count spike. And to the extent that the surge in cases are "probable" and not even confirmed, we could be looking at a lot of smoke without any fire.