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As epidemic trajectories in Europe rise back towards their spring peaks, a thread on normalisation during a pandemic... 1/
In late Feb & early March, we modelled scenarios for what effect widespread social distancing measures might have in UK. Like others, we'd already modelled contact tracing ( https://www.thelancet.com/journals/langlo/article/PIIS2214-109X(20)30074-7/fulltext) but characteristics of infection suggested additional measures would be needed. 2/
At the time we were doing this modelling, fewer than 3000 COVID deaths had been reported globally (below from 1st March). I remember doing media during this period and could tell many saw the potential impact of COVID-19 as rather abstract, given observed numbers to date... 3/
In our analysis during that period, we considered a range of measures, including self-isolation when ill, shielding of older groups, school closures, social distancing... Two crucial factors influenced these scenario estimates: severity & transmission dynamics. 4/
Early severity estimates using traveller testing ( https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30243-7/fulltext) and age-adjusted patterns from Diamond Princess data ( https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2020.25.12.2000256) put IFR at 0.6-0.7% in China. UK has similar, albeit slightly older demography, which would mean similar IFR. 5/
Using age structured transmission models, accounting for differences in contact structure between home/work/school etc, Imperial ( https://www.imperial.ac.uk/mrc-global-infectious-disease-analysis/covid-19/report-9-impact-of-npis-on-covid-19/) and LSHTM ( https://www.thelancet.com/journals/lanpub/article/PIIS2468-2667(20)30133-X/fulltext) concluded that uncontrolled epidemic could lead to hundreds of thousands of deaths. 6/
Many commentators subsequently focused on these big numbers in the 'do nothing' scenarios, but in scenarios where lockdowns were triggered once given number in ICU, estimates were much lower - some point estimates even lower than the subsequent reality. 7/
Some disagreed with these assumptions, claiming IFR actually as low as ~0.01% (e.g. https://unherd.com/2020/05/oxford-doubles-down-sunetra-gupta-interview/), which implied couldn't have many deaths. Arguments have since shifted – while virus has continued spreading, indifferent to claims otherwise: https://twitter.com/AdamJKucharski/status/1308350331231797248?s=20 8/
But here we are again, with deaths across Europe rising - numbers that were once thought astonishing, and are now seen by many as normal. So I think it's important to occasionally reflect on this transition, and how once big numbers came to feel so small. 9/9
