Somewhat to my surprise this late in the pandemic I'm, still seeing 'cases may be rising but hospitalisations aren't' so I thought it would be useful to do a broad timeline of the delays between infection & the various stats warning us. They can run into weeks /1
1. Infections are invisible, we don't know they have happened, no test can pick them up until some days later. Delta has been observed to double in 4.5 days meaning by the time we have a clue 1000 infections are already 4000
2. Cases are when someone has felt ill or has been told they are a close contact, booked a test, attended the test, the swab has gone to a lab, the lab has got a result & that result is Quality assured. It varies with the speed of those steps but Cases are probably 9+ days
3. Hospitalisation generally doesn't happen until the 2nd or 3rd week after infection. And generally hospital numbers are for the day before the current one or to early that morning. So perhaps 15-22 days post infection, 1000 Delta may be 16000 by now
4. Deaths average at around 21 days post infection however the notification process may be very slow, in Ireland it may take 3 months. Deaths in a hospital setting are faster but even there our 1000 Delta is nearing 32000 by notification
5. However mostly daily stats are not used for policy decisions - average of 1 or 2 weeks used (7 or 14 day incidence per 100k population). This stops numbers randomly bounces around but it does add another delay before a problem becomes apparent which I'll show by example next
14 day incidence of deaths per 100k at 10 a day for 14 days. From day 15 it increases to 150% of the previous day, 15 deaths but the rate is now only 10.04. Day 16 its 23 but the rate is only 11.3. Day 17 its 35 & rate is 13.1, a clue something is up. 1000 delta is now near 50k
If you tell politicians we need to close because the death rate has gone from 10 to 13 they may well say that doesn't sound like much and we can't meet for 5 days, lets decided then. Delta is now near 100k and a huge number of extra deaths are built in
The only way of acting somewhat early is to understand the current percentage of cases that will become hospitalisations and act on the basis of those case numbers. At the moment in Ireland our hospitalisations each week are 2% of the cases in the week to 6 days previously
Vaccinations are working & working powerfully but most people are still not fully protected. True often from the groups who were less likely to be hospitalised by Covid. But its still going to be a percentage of cases just a lower one - tracking that here
https://twitter.com/andrewflood/status/1407357458243280900?s=20
BTW we are seeing something very close to this timeline play out in data from the north, itself a week behind the data playing out in England and Scotland. For 10 days nothing happened, then cases rose but not hospital admissions, now hospital admissions rise
Hopefully vaccination has driven deaths down from 1% of exposures leading to infection to 0.05% in which case deaths should remain rare. But hospitalisation is still a severe outcome & if cases rise high & hospitalisations follow will mean once more other care is cancelled
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