[Epistemic Status: It's easy to be fooled by randomness in the coronavirus data but the data and narrative below make sense to me. Overall, I'm about 70% confident in the actual claim. ]

Iran's recent worldometer data serves case study demonstrating relationship between sufficient testing and case-fatality rate. After a 16 day long plateau (Mar 06-22) in daily new cases which may have seemed reassuring, we've seen five days (Mar 24-28) of roughly linear rise. We could anticipate this by noticing that in a similar time frame (Mar 07-19), we were seeing a linear rise in case fatality rate before it became constant. This indicates the following narrative (not sure if it's actually true):

  • Coronavirus spreads uncontrolled in Iran without increased testing capabilities. This causes new daily cases to stay constant despite increased infection -- the 16 day long plateau in daily new cases
  • Because cases are increasing, the number of severe cases is also increasing - - and severe cases are more likely to get tested than less severe cases. This causes fatality rate to rise as the severity of the cases that are actually tested increases -- the 12 day linear rise in case fatality
  • Recently, testing capabilities were ramped, allowing testing of more people and the observation of less severe cases. As a result, the number of daily cases started increasing again with the testing rate. Simultaneously, the fatality rate plateau'd as the (complex) trend in severe cases being tested in greater proportion to less severe cases was cancelled out by trend in testing. Hence the last five days of daily new case rise and the past eight days of constant fatality rate.
    • Note that this narrative suggests that testing is being continuously ramped up while remaining the bottle-neck. Two pieces of evidence for this:
      • The daily cases start increasing linearly from the plateau. If testing was increased dramatically, one would an immediate discontinuous increase in number of daily cases at the point where more tests are done.
      • Iran's death rate is still much higher (17% compared to an IFR which should be less than 5%) so testing is unlikely to be sufficient to capture the true infection rate

March Coronavirus Open Thread

by Elizabeth 1 min read8th Mar 2020377 comments


This thread was created on 3/8/2020, or approximately one million years ago in virus time. It’s getting pretty bloated now, and a lot of things that were high value at the time have been eclipsed by events, making karma not a very useful sorting tool. So I’m declaring this thread finished, and asking everyone to move over to the April Coronavirus Open Thread.

Interested in what happened in this thread? Here’s the timeless or not-yet-eclipsed highlights:

  • Scott Alexander comes up with Hammer and Dance 6 days before Tomas Pueyo
  • Spiracular on why SARS-Cov-2 is unlikely to be lab-created.
  • Two documents collating estimates of basic epidemiological parameters, in response to this thread
  • Discussion on whether the tuberculosis vaccine provides protection against COVID-19.
  • Suggestive evidence that COVID-19 removes sense of taste and smell.
  • Could copper tape be net harmful?