The U.S. now stands at 28.5 new cases per 100K per day, up 32% in the past seven days. That’s up from 26, as of last Friday’s reading.
Data source for this and other graphs of new case counts: Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 5/17/2022, from https://github.com/nytimes/covid-19-data.” The NY Times U.S. tracking page may be found at https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html
It seems that the U.S. is going to be taught another practical lesson in the magic of compound growth rates.
The graph above is a “log-linear” graph. A constant growth rate will graph as a straight line. That’s pretty much what we’ve had, for the U.S. average new cases per day, for just a bit over two months now. A constant 25 percent per week increase in daily new COVID-19 cases.
If you just assume a few more weeks of growth at this rate, and the new case count for the Omicron-II wave (BA.2.12.1) will soon top all the U.S. COVID-19 waves prior to Omicron.
How many weeks, you ask? Four. At a steady 30 percent per week increase, the official new case count for the Omicron II wave will top all waves prior to Omicron I four weeks from now.
Of that four weeks, two are already locked in, owing to the various lags (between infection, symptoms, care-seeking, testing, reporting, and a seven-day-moving average). What we’ll see in the numbers, two weeks from now, are the infections that are taking place today.
Obviously, that raw new-case count is nowhere near as serious for Omicron II as it was back in the (pre-vaccine) winter of 2021. With high levels of some form of immunity in the population now, the same case count will lead to far fewer hospitalizations and deaths.
But, as with the Omicron I wave, if you pile up enough new infections, it’s going to start to make a dent in things. Not just for the impact of mass absenteeism on business in general. Not just for the specific impact on industries that require large indoor public gatherings (e.g., live entertainment, restaurants). But, eventually, for the health care system, as hospital ICUs begin to re-fill with (mostly un-vaccinated, elderly) COVID-19 patients.
But that’s next week’s problem. If it occurs.
BA.2.12.1 is not yet the dominant strain in the U.S.
The CDC released this week’s estimates today, and they estimate that BA.2.12.1 still does not account for the majority of new U.S. cases. They’ve reduced their estimate of the growth rate (now down to just 22% increase per week), and that knocked down their entire set of projections.
This week:
Last week:
Source: CDC COVID data tracker, this week’s data accessed 5/17/2022.
It’s no huge surprise that there might be some revisions. The CDC “Nowcast” number is actually a projection based on the known level and growth of cases three and more weeks in the prior. So the CDC is always in the position of projecting a fast-growing series forward, based on historical case counts.
The practical importance is that, all other things equal, we should expect the growth in the daily new case rate to accelerate, going forward. We’re in the process of replacing an incredibly infectious Omicron (BA.2, R-nought of maybe 15), with an even-more-infectious Omicron II (BA.2.12.1).
Finally, despite the growth of new cases, and now the likely acceleration of that growth, there’s still no hint that people are responding to that in any way. Using mask use as the measure of COVID-19 hygiene, the U.S. is, at best, flat. Even in Massachusetts — nearing 70 new cases per 100K per day — there’s no discernible uptick in mask use.
Source: Carnegie-Mellon University COVIDcast.
In large part, that’s reasonably rational. We’re still just above 300 deaths per day, and we still have not reached 3000 new hospitalizations per day. I expect we’re going to see little to no reaction to the Omicron II wave unless and until some widespread and serious health consequences arise. And if that never happens, then ignoring it — as we routinely ignore seasonal flu — would be no more irrational than our approach to seasonal flu.
