How different would the global dynamics have been if COVID-19 had instead been a pandemic flu virus with similar fatality rate? A few thoughts... 1/ https://twitter.com/AmandaKvalsvig/status/1334210156071055361

There are differences between pandemic flu and SARS-CoV-2, of course. In absence of control, serial interval for SARS-CoV-2 ( https://science.sciencemag.org/content/369/6507/1106) is longer than flu ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3057478/), and evidence SARS-CoV-2 transmission more clustered ( https://www.sciencedirect.com/science/article/pii/S1201971220305117) 2/

The susceptibility profile may also be different. In flu pandemics, susceptibility is often concentrated in younger groups ( https://pubmed.ncbi.nlm.nih.gov/20096450/ ) - for COVID-19, severity/susceptibility concentrated in older groups (e.g. https://www.nature.com/articles/s41591-020-0962-9). 3/

A few countries (e.g. South Korea & Japan) have used targeted approaches that account for the clustered dynamics of COVID-19, but many around the world have not (or at least not yet effectively):
https://twitter.com/AdamJKucharski/status/1293472353758871552?s=20 4/

Many of measures currently being deployed - such as shutting down segments of society - come from the 1918 toolkit, which is why many of the debates are so familiar: https://twitter.com/AdamJKucharski/status/1279343550161920001?s=20 5/

Indeed, the approach of shutdown-type measures + strict border restrictions would likely work against pandemic flu - we know this because these measures have also suppressed the 2020 flu season in many places (e.g. https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciaa1475/5912591) 6/

It's tempting to put control measures in 'flu' boxes and 'coronavirus' boxes, but I suspect the global experience with COVID will also make many countries rethink their plans for a future severe flu pandemic. 7/7