A thread on projections for the fall-winter wave. In this thread I will present a best-case scenario and worst-case scenario. 1/
First, we need to assess current conditions, which plug into the analysis. New cases are plateauing at ~40k heading into the fall.
Mask use is declining slightly.
Social distancing is declining slightly.
Ok now let's compare current conditions with the period before the summer surge (May).

On the one hand, there is now slightly more mask use (but on the decline) and more immunity from infections. BUT...
Now there is:
- less social distancing
- schools and colleges reopening
- seasonality of the virus (lower humidity, more people coughing and sneezing)
- higher baseline incidence
Let's call these factors a wash. In reality, the downside factors seem like they will overwhelm, but call it a wash. From the summer trough to the summer peak, actual infections were +137% (derived from deaths).
Now apply this epidemic curve to the fall from a baseline of 40k (confirmed) cases today. You get an explosion to 97k (confirmed) cases per day in November.
Ok now let's look at a best-case scenario. For this I will use the best-performing model. But first let's take a look at the limitations of models.
These model projections only go through Sept. 26. They do not incorporate Labor Day as a super-spreading event; changes in social distancing; or seasonality.
The best-performing model, by @youyanggu, projects new cases on Nov. 1 that are 88% of today, but trending upward. So this is my best-case scenario -- pretty much what we are facing today.
Why do I believe this is a best-case scenario? The model assumes behavioral change in response to rising cases will flatten the curve. And this is what happened to some extent in the summer. BUT...
Exponential spread is...exponential. Put it on top of a much higher baseline incidence, and the curve could take off. People may react, but it may be too late.

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More from @TopherSpiro

6 Aug
The U.S. does not have a strategy to contain the virus. Here is a new strategy based on our comprehensive review of the evidence. From @EmilyG_DC @NicoleRapfogel @maura_calsyn and me
@EmilyG_DC @NicoleRapfogel @maura_calsyn 1. Cluster-forming venues should be closed in areas with a positive rate above 2 percent. These indoor settings where people congregate include bars, nightclubs, indoor dining.
@EmilyG_DC @NicoleRapfogel @maura_calsyn Indoor social gatherings of more than 10 people should be banned. If restaurants reopen in areas with a minimal positive rate, federal funding should help them meet air quality standards, such as the use of portable HEPA air filters.
Read 14 tweets
11 Jul
Now that everyone better understands airborne transmission, I want to lay out a hopeful near-term strategy that should be feasible. 1/
Up to this point, most of the focus has been on individual-scale response or community-scale response. But there is something important in between. 2/
We know from the research of @AdamJKucharski that a small number of super-spreaders are responsible for the vast majority of cases. We need to focus on clusters and settings that breed clusters. 3/
Read 14 tweets
4 Jun
Arizona is in real trouble. New cases and positive rate rising steadily.
Florida’s positive rate is on a clear upward trajectory.
Georgia’s positive rate is spiking.
Read 12 tweets
2 Jun
Cases in Texas are on the rise. So is the positive rate.
The positive rate is spiking in Florida, @SeanTrende
Look at this. Outside of NY, NJ, CT, cases are steady and even rising.
Read 11 tweets
26 May
THREAD: COVID situational update, May 26
Outside of the NY metro area, new cases have flatlined, with some possible emerging decline in the last day or so.
Testing is down; while the positive rate was slowly declining, it has now leveled out. Worrisome.
Read 9 tweets
26 May
Current status: the worst of both worlds.

People are still scared, so won’t fully restart the economy.

But enough will go out to seed outbreaks and ongoing transmission.
Let’s call this Trump’s half-baked, muddled, non-policy. The result is almost like Sweden, without realizing that’s what you’re doing. Many will needlessly die as a result.
We could have gone into the fall with low baseline incidence. We could have locked down more strictly for a shorter time and crushed the virus. Some states have done better than others, but interstate travel will limit their success.
Read 4 tweets

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