We still seem to be on hold here in the U.S. We remain at 33 new cases per 100K population per day. That’s about where we’ve been for the past three weeks. The seven-day percent change isn’t really meaningful owing to the impact of Memorial Day on the data.
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 6/9/2022, 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
That seemingly-steady figure is the result of offsetting trends across the regions. Just by chance, declines and increases in new cases have been more-or-less in balance since about the third week in May.
If this were merely a case of letting the internal dynamics of the pandemic play out, we could take a typical top of a wave, superimpose that on the current data, and take a guess as to where we’re heading over the next few weeks. If there were no changes, it would just be a matter of time before everyone who is likely to get BA.2.12.1 has done so, and the wave peaks. In the past, I did that sort of simple-minded prediction to good effect at the end of the winter 2021-22 (Omicron-I) wave, when the main driving force was Omicron simply running out of new people to infect.
Peak of the winter wave:
But now we’ve got yet another set of variants on the horizon. I skipped right over this the last time I put up the CDC data, because I was still looking to see how fast Omicron-II (BA.2.12.1) was spreading. But these yet-newer variants are making the headlines, so it’s time to see what fresh hell awaits with BA.4 and BA.5.
These are shown at the bottom of the most recent graph of variants from CDC:
Source: CDC COVID data tracker, annotations mine.
The Omicron family tree
This is a brief review of nomenclature, a.k.a., where did BA.4 and BA.5 come from? It’s just a way to stay oriented, instead of treating all of these variants as if there were random draws from some alphanumeric soup. You may want to refer to the graph above as I walk through this.
I went through the naming rules for COVID-19 strains, in detail, in Post #1433.
The original successful natural strain of COVID was termed “B”. (Strain A was unsuccessful.) Every significant mutation gets its own numerical suffix, numbered in the order they were identified (e.g., B.1). Every sub-mutation gets yet another period, and another number appended.
There is an international organization in the background that keeps all of that straight, so that the entire world uses the same numbering system.
Then, in a much hazier process, Greek letters get assigned to variants (and their descendants) that spread widely and/or seem to be of particular concern, and that appear to have otherwise similar characteristics. So the Greek letters should be thought of as the prominent families within the overall COVID-19 population. While the letter-and-number names are the individual family members.
Hence, the original Omicron, B.1.1.529, is a great-grandchild of the ancestral COVID-19 lineage give the name “B”. The first-ever variant of B that was identified was B.1. The first sub-variant of B.1 to be identified was B.1.1. And the 529th variant of B.1.1 to be identified was B.1.1.529.
They only allow three suffixes. After that, they assign a new letter-combination to that four-node strain, and repeat the process from there. The actual letters assigned are completely arbitrary, given in the order the variants are discovered and named. You have to consult a look-up table to see all the “aliases” — what four-node names got renamed — available at this reference.
Once the original Omicron began having significant mutations, they assigned B.1.1.529 the new name BA, and kept going. So BA.1.1 is the first significant grandchild of Omicron. Hence:
- B.1.1.529 = BA
- B.1.1.529.1.1 = BA.1.1
- B.1.1.529.2 = BA.2
- B.1.1.529.2.12.1 = BA.2.12.1
All of these (listed in the graph above) are considered branches of the Omicron family, as they all derive from mutations of the original Omicron (B.1.1.529) and all appear to have clinical properties similar to the original Omicron.
And so we immediately learn that BA.4 and BA.4 are brand-new branches of the Omicron family. They are the fourth and fifth significant mutations of the original Omicron virus (B.1.1.529).
- B.1.1.529.4 = BA.4
- B.1.1.529.5 = BA.5
What’s the buzz on BA.4 and BA.5?
Without bothering with references, let me distill what I think I just read.
Both of these arose in January 2022 in South Africa. Both have spread widely. Both appear capable of becoming the dominant strain in an area. Neither one appears any more dangerous or any more contagious than the existing Omicron strains. But both are better at re-infecting individuals whose only immune protection comes from a prior Omicron infection.
So, reading between the lines, these appear to be filling the vacuum left in the wake of the large Omicron wave. Based on what I’ve read, these aren’t as good as the original Omicron or BA.2.12.1 at avoiding the immunity caused by vaccines. But they have an enhanced ability to get around the immunity offered by a prior Omicron infection.
The size of the original Omicron wave (U.S. winter 2021-22 wave) means that there’s a significant fraction of the population susceptible to a re-infection from BA.4 or BA.5. That consists of unvaccinated individuals who were infected during the Omicron-I (winter) and Omicron-II (spring) waves.
My take on it is not that BA.4 and BA.5 mutated to avoid that prior immunity. It’s that we’re seeing these preferentially transmitted in the population because they have a larger pool of potential targets available to them, versus strains that can’t avoid the immunity generated by Omicron.
When I boil it down, it seems like BA.4 and BA.5 are just business-as-usual variants. Nothing like the sea-change that occurred when Omicron took over from Delta by being three times as infectious. These seem to have the sole advantage of being able to reinfect those who aren’t smart enough to get vaccinated, and got infected in the last wave. But in America, that’s enough of an advantage that they’ll likely take over from the current dominant strain BA.2.12.1.
For sure, these arose in South Africa, and the impact on South Africa does not appear to have been devastating:
Source: Johns Hopkins data via Google Search.
These new strains are reported to have become the dominant strains in Portugal. Again, like South Africa, that doesn’t seem to have led to anything out of the ordinary:
The upshot is that these are new strains within the Omicron family. And they will likely take over because they are good at re-infecting un-vaccinated individuals who have only had a prior Omicron infection.
Maybe we’ll get another ripple on the existing Omicron-II wave out of this. For sure, there’s nothing to suggest a return to new-case levels seen in the Omicron-I wave.
The final bit of good news is that these latest strains appear aimed largely at the un-vaccinated. They don’t seem to be good at avoiding immunity provided by vaccination. That seems fair to me.
