That is why the size of the wave is probably more important than the severity of the strain. And why the most important thing to sort out right now about the ongoing wave is why South Africa turned so quickly and so sharply. And why it may be very good news that in many places the Omicron curves appear to be already turning or perhaps about to: in Norway, for instance, total case numbers appear in decline, while elsewhere in Europe and the U.K. case growth is slowing or even plateauing. Summarizing the recent data on Twitter, Bedford wrote, “Omicron wave will be fast and intense across geographies, but is expected to burn through quickly,” though he also warned that, “even if individual potential of severe outcomes are lower for Omicron, regions with already strained hospital capacity are particularly at risk.”…

What could explain rapid turns like that already taken by South Africa? And how confident should we be in projecting that it is replicated in the U.K. and the U.S., for instance, or countries with much different immunological profiles? It’s not entirely clear, but for once in the pandemic, the mysterious, animal spirits of disease spread may be working in our favor — in some cases seeming to reduce that initial reproduction number as much as four-fold within a week or two and without anything like the heavy-handed shifts in public policy or panicked disruptions to social behavior that have, in the past, tended to produce smaller reductions in rate of growth.

And a few particular hypothetical possibilities hover on the horizon, probably none a total explanation, and perhaps some not contributing any effect at all — only time and much deeper analysis will tell. If it turns out that Omicron has a much shorter generation time (meaning not that each case infects more additional people but that the infection turnover happens more quickly), that might mean that the initial reproduction number was not as high as originally thought — and can help explain rapid turns for the better as well.