7/n But what does that say about cases? Well, we can actually use these death figures to (VERY crudely) back-calculate an estimate of the number of cases each week in the US by age
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8/n Using our age-stratified IFR paper, we can (again VERY CRUDELY) estimate cases by saying: IFR = deaths/true cases => true cases = deaths/IFR https://www.medrxiv.org/content/10.1101/2020.07.23.20160895v6 …pic.twitter.com/Wxpf2RPHhS
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9/n If we plug these deaths and age-stratified IFRs into our equation, and assume that there is a median ~30 day lag between infection and reported death, we end up with a graph that looks like this for cases Not as different as before!pic.twitter.com/u2GPqrbnT6
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10/n Now, as I've repeatedly said, this is VERY CRUDE For example, deaths are so rare in the under-5s that it's hard to estimate any realistic number of cases in this age group. It's likely that they are underrepresented to an extent
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11/n But we can go further even than this. What if we graphed the PROPORTION of infections in each age band, inferred from deaths? It looks something like this Now the waves barely look different at allpic.twitter.com/IozFDdIxpu
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12/n In particular, if I put the two graphs side-by-side, you can see how a TINY change in the proportion in older people being infected can lead to a HUGE numerical increase in deathspic.twitter.com/QUyfQQh9z7
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13/n But broadly speaking, using this (again, VERY CRUDE) method, there appears to be little difference between waves 1 & 2 in the US It's simply that our testing changed, not that the disease itself was different
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14/n Indeed, as you can see, the FIRST wave in the US PROBABLY HAD MORE CASES THAN THE SECOND despite having fewer confirmed casespic.twitter.com/20lUU4KuOR
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15/n Interestingly, this also gives us a very crude number of total cases in the US roughly in line with
@youyanggu's modelled estimates, with about 12-15% of the country infected by late September5 replies 2 retweets 38 likesShow this thread -
Replying to @GidMK @youyanggu
There is also another important takeaway specifically for the US. Each State had a different dynamic so all in all the averaging effect is not something that should be taken lightly either. Agree with you, there is no evidence the disease had changed at all.
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Yes absolutely. I suspect that the peak in the first wave was early March and probably almost entirely centred in the North East, while the second wave was much more spread out across the country and had a longer peak that led into the third wave
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