Thread by @mbeckett

The trillion dollar question. Why are COVID cases increasing while deaths are decreasing? The answer is simple. It's called Simpson's paradox and it's the result of incorrectly pooling data and arriving at a false conclusion. A thread 1/9 #COVID19 #ThursdayThoughts

2/9 If you lump the data and look at the US as a whole, you'll observe: Cases are increasing, positivity rate is increasing, hospitalizations are increasing, and deaths are decreasing. Until recently, it also looked liked hospitalizations were decreasing and positivity was flat.

3/9 It would be rational to come to the following conclusions. "Young people are getting it now, not old people." "We've gotten better at treating it, the death rate has fallen." "We're testing more people, so we're seeing more cases." Twitter is awash with these.

4/9 There's some truth to these conclusions. Yes, more young people than old are getting it (for now). Yes, we have gotten better at treating it (a little). Yes, we are testing more people and finding more cases (somewhat). None of these conclusions explain the effect.

5/9 Here's the truth. The COVID-19 outbreak, is not ONE outbreak spread evenly across the US. It is MANY outbreaks spread unevenly. You need to look at state data, or better, county data to really understand what's going on.

6/9 For instance, take AZ and TX. Cases AND deaths have both been increasing for weeks. FL looks similar (except their data sucks, so it's hard to analyze precisely). If you cone in on Miami and Houston, it's much worse.

7/9 This is the heart of Simpson's paradox. If you pool data without regard to the underlying causality, you'll get erroneous results.

8/9 The truth is simple, and horrifying. We are about to have dozens of NYCs around the country. The next 8 weeks are going to brutal, no matter what we do. ICUs overflowing, ventilators rationed, hundreds of thousands of deaths.

9/9 Unfortunately, the virus is still here and we've failed to manage it with mis-step after mis-step since the beginning. I have no agenda. I'm a doctor, a scientist, a tech founder, a husband, and a father. I'm simply sad that it's come to this. Stay safe.

Woah, this went viral. I hope it makes a difference. As I said, I have nothing to promote. Please wear a mask, socially distance, and stay safe. Most importantly, be kind to one another. We’re all in this together.

UPDATE 1 WEEK LATER 1/5 Trends are all unfortunately moving in the expected direction. If you look at overall US trend, states/counties with growing outbreaks are overwhelming declines seen in the NE. Deaths are starting to spike nationally, and 7-day average is creeping up.

2/5 If you separate out states with the most active outbreaks and compare them to all other states lumped together, the grim trend is clear. Deaths are increasing in states with the most rapidly expanding outbreaks (AZ, TX, FL). CA and others are close behind.

3/5 Diving into AZ, TX and FL specifically, it's clear that increased cases are driving increased hospitalizations and increased deaths (each with a time lag).

4/5 AZ ICUs are at 89% capacity. FL adult ICU beds are at 100% capacity at 44 hospitals. There is more data that collectively circles around the same message. Hospital systems are within weeks of being overwhelmed in multiple counties and states.

5/5 In POSITIVE news, counties and states are starting to listen. Mask-wearing is being better enforced, re-openings are rolling back, and hospitals are working to increase capacity. Hopefully these measures will help, but it might already be too late. Time will tell. Stay safe.