COVID-19 Watch

Over the last week we have been talking about the mystery of second wave resistance across the US. After about 25% of the population is infected and recovered, there is remarkable resistance to a resurgence of the virus, even after states "reopen". This is mysterious because immunity thresholds should be around 66% if the R0 of SARS-CoV-2 is really around 3 as we believe. One likely explanation for this is that personal behavior is providing the additional protection. In the past I have used Google mobility data to characterize the level of physical distancing. But this only captures how much we are moving around, and can't capture how careful people are being. However, there is now some interesting polling data available that may capture some of these effects. Ryan Burge has provided excellent visualizations of the steps the American public is taking from the DFP COVID-19 Tracking Poll: (see: https://twitter.com/ryanburge/status/1301887909675569152/photo/1 ) Approximate...

 Today the USA passed 200,000 deaths.  World wide we are nearly at 1 million deaths.  Source: https://www.worldometers.info/coronavirus/country/us/   Early predictions back in March were that between 100,000 to 200,000 people might die from COVID-19 in the USA if we did nothing.  We didn't do nothing. But what we did was just as ineffective.  Now over 200,000 are dead, worse than the worst of the projections. There is a narrative that these projections were wrong... too "high".  It turns out that they were actually far too low.  They were wrong, in other ways. The assumed fatality rate was too high in the early models, but they under-estimated how many would be infected. They over estimated how quickly the disease would decline, and they severely over estimated the quality of our response. We failed, beyond the wildest imaginings of the worst case models from March. 

Yesterday we discussed regions that were initially hard hit , to determine how resistant some of those places have been to a second wave, places like New York, Spain, France, and Italy.  Today we want to discuss regions that were not initially hard hit, where immunity levels are very low, and the virus has a lot of room to spread if it were to get out of control there.  Excellent examples of this would include New Zealand, South Korea, and even China, where their vigorous response prevented the virus from spreading extensively beyond Wuhan. Each of these countries, in their own way, demonstrated that failure was not inevitable, and that it was possible to control (and even completely eliminate) the virus. They also demonstrate that the economic cost of COVID-19 was best minimized by first aggressively controlling the virus.  However, recent rises in cases brought this narrative into doubt. In July/August each country saw new cases rise again. And with an almost entirely ...

Predictions of Rt in the USA as a whole continue to be below 1 (currently 0.985), meaning that the rate of new cases are decelerating (you can thing of Rt as an estimate of the acceleration):  Despite this fact,  IHME is now predicting over 400,000 deaths by the end of the year, because of a proposed large second wave coming in the fall. But if new cases are currently slowing down, why would they predict that they would rise again in the fall?  Other historically more accurate models do not predict this same large second wave. IHME is predicting that daily deaths will rise between now and November, while COVID-19 Projections predicts that they will fall between now and November 1st.  The issues revolve around the surprising resistance to second waves that we have already seen in hard hit locations around the world. For example, in the US, the second peak of infections after the lockdowns were eased all happened in locations that were not initially hard hit.  T...

It's been a few weeks since I have done a simple status update.  World Wide: Yesterday the official death tole passed 900,000. They past 800,000 on the 21st of August, only 18 days ago. Daily deaths were falling slowly, but are back up now to roughly where they were. The longer term trends is that they are mostly holding steady at around 5,500 / day: Cases were falling slowly, but are back up now:  And that means that the daily change in the number of active cases is now positive again after briefly dipping into the negative territory. That means that there are more people actively infected today than there were yesterday, and that the spread of the disease is speeding up.  USA: Rt.live does not run their algorithm on the US as a whole, but when I do that, I find that the Rt for the US is 0.95, so new cases in the US are falling.  Daily deaths in the US remain high, but are also falling:  The 7 day average is being impacted by a holiday weekend again, and is not...

Last week I wrote about how there have been surprisingly low cases are not climbing again in many locations that had a high first wave of disease. Most of the "second peak" of cases in the US were coming from new locations, which did not see an initial first wave of infections. I discussed why that was surprising, and gave several theories for why this might be happening.  This week, we need to revisit that, and discuss regions which were hit hard early on, but where cases are, indeed, starting to rise a second time.  One location like this is New York:  Daily new cases there appear to be on the rise again, and this does not appear to me to be due to increases in testing. Estimates of Rt in NY yesterday put it at around 1.06, and possibly climbing. On the whole, cases are still falling in the US, with an Rt estimate of 0.96. Before now, New York has consistently had a lower Rt than the rest of the US, but that is no longer the case.  We can see even more pronou...

  In the last update, I promised that I would talk about immunity levels in the population next. I'm going to do that today, but I want to first show why it matters.  IHME vs. Youyang Gu, the Battle of the Models: The IHME model is now predicting 410,451 deaths in the USA from COVID-19 by the end of the year. They are making this prediction based on the assumption that there will be a large second wave in the fall, that is larger than either the first or the second peak in infections:  In contrast, Youyang Gu's model predicts no such thing. Unfortunately, Youyang Gu's model only predicts out to November 1st, and the large second wave predicted by IHME happens after that. The two models aren't really all that different up to November, and Youyang Gu refuses to predict anything further out because he claims (with good reason) that no one really knows what is going to happen that far ahead.  But even so, he's predicting a decline in daily deaths, while IHME is pr...