Thread by @trvrb

I'm re-upping an analogy from Feb 2020 for how to think about epidemic spatial spread as Omicron is detected across the world. 1/6

https://twitter.com/trvrb/status/1226241415522373632

Omicron appears to have emerged around Oct 1 and has taken 8 weeks of exponential growth to "suddenly" have sizable impacts on case counts and hospitalizations in Gauteng. This "suddenly" is the nature of exponential growth. 2/6

https://twitter.com/trvrb/status/1466076787381727233

Exports from the South African epidemic are now being detected across the world and these exports are sparking local transmission. Figure from nextstrain.org/groups/blab/nc… using data generously shared to @GISAID. 3/6

As a broad analogy if it took ~8 weeks for Omicron to grow from initial spark into local epidemic in South Africa, I would expect very roughly 8 weeks from today for secondary epidemics to begin to manifest. 4/6

This is assuming rate of spread is similar across populations, which may not be the case. Population immunity differs quantitively (proportion with some immunity) and qualitatively (vaccine derived vs infection derived) across geographies. This may well impact rate of spread. 5/6

I expect we'll know more about the extent of worldwide seeding and epidemic growth rates in different geographies in just a couple weeks. 6/6