Thread by @trvrb

The extremely rapid rate of spread of Omicron clearly visible since the beginning of December will now be acutely felt in many geographies as local epidemics amplify to the point of eclipsing Delta circulation. 1/12

https://twitter.com/trvrb/status/1467245887357210624

Continuing previous methods, if we partition case counts from @OurWorldInData using sequence data from @GISAID and apply a modeling approach from @marlinfiggins we get rapid rises in Omicron cases in South Africa, Denmark, Germany, the UK and the US. 2/12

This corresponds to rates epidemic doubling of between 2.3 days in the UK and 3.3 days in Germany. 3/12

However, this approach of using sequence data is necessarily lagged by timeline for genomic sequencing. We can get a more recent picture by looking instead at PCR testing results that distinguish between probable Delta cases and probable Omicron cases via SGTF. 4/12

London as expected from travel connections appears to be ahead of the rest of the UK and much of the rest of Europe and the US with 72% of specimens from Dec 13 as probable Omicron in a remarkable rise. 5/12

https://twitter.com/theosanderson/status/1471537690650812420

With Omicron comprising the majority of SARS-CoV-2 in London, we can now expect its continued spread to manifest as skyrocketing case loads. Figure from coronavirus.data.gov.uk/details/cases. 6/12

The UK has a systematic effort to track and record SGTF that's lacking in the US. We do have particular local efforts to track this however. Close to home, we have @UWVirology and @seattleflustudy tracking probable Omicron via S gene presence/absence. 7/12

https://twitter.com/pavitrarc/status/1471161839534809091

In combining datasets, we can see rapid logistic growth of probable Omicron tests in King County. 8/12

Partitioning King County cases by these proportions shows a rapid exponential rise in Omicron cases in King County with a 2.2 day doubling. 9/12

There is potential worry that tests performed by @UWVirology and @seattleflustudy won't be fully representative of the county, but pace of doubling fits what we've seen elsewhere and with spread this fast a slight difference in prevalence will only push things slightly. 10/12

If we do a very simple 10-day projection of this rate of growth we get ~2100 daily Omicron cases in King County on Dec 22. This is ~3.5 times the Delta peak in King County in August and this is only 1 week away. 11/12

I expect case loads to climb suddenly and rapidly in a large number of well connected cities over the next week. This will take many by surprise but was baked in as soon as we knew Omicron Rt. 12/12