Coronavirus scoreboard for August 9: BA.5 dominant, slowly declining;  endemicity model

– by a New Deal Democrat



BIobot’s latest update, as of last week, shows a 15% drop in COVID in wastewater, consistent with about 460,000 “true” new infections per day:

All 4 census regions (not shown) are participating in the decline.

Confirmed cases (dashed line below) fell by roughly a similar percentage, to 105,500. Deaths (solid line) are near a 4-month peak of 489:

Hospitalizations have held for the past 3 weeks at around 44-47,000, and were 44,800 yesterday (last year shown for comparison):

In the meantime, the CDC has updated its information on the variant. BA.4,4.6 and 5 now account for 98% of all infections. BA.5 slightly increased its share from 84.5% to 87%. BA.4.6 did not significantly increase its share:

It does not appear that BA.4 or BA.4.6 will make significant inroads into the dominance of BA.5, although BA.4.6 accounts for over 10% of infections in the High Plains (regional map not shown). BA.2.75 does not appear at all.

With no new variant ready to overtake BA.5, I continue to suspect that there is further slow decline in cases in the near future, which will soon manifest itself in lower hospitalizations and then lower deaths.

Finally, Trevor Bedford has a very informative thread on what endemic COVID is likely to look like based on the rate of mutations and the length of time that a previous infection makes a recovered person resistant to re-infection.

Here are a few highlights:

“Based on the experience in the winter of 2020/2021, the seasonal impact on SARS-CoV-2 transmission is quite clear…

“we can gain some intuition from simple epidemiological models…

“Specifically, we can use a SIRS system where individuals go from susceptible to infected to recovered and then back to the susceptible class due to immune waning/virus antigenic drift….

“ with a flu-like ~5-year decay rate (in blue) we get winter epidemics and summer declines, while with faster decay we see higher circulation levels and less variation between winter and summer (in yellow and red )…

“If what we’ve seen with the Omicron evolution in 2022 becomes largely the norm, then this result would represent a ~24% reduction within ~6 months, or a very rough reduction from R→S on a time horizon of ~1.8 years, i.e. near the yellow curve in the above SIRS model.”

He points out that he is not making a prediction, but rather

“illustrate a scenario where we end up in a variant-driven year-round circulation regime, with more circulation in winter than summer, but no flu-like winter seasons and summer dips.”

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