#17,050
BA.5 has remained the dominant COVID strain in both the UK and the United States since June - an unusually long reign for an Omicron subvariant (15+ weeks) - which tend to follow a faster replacement cycle than earlier strains (Alpha, Delta).
While BA.5 remains firmly entrenched in both nations, there are subtle signs of erosion, with BA.5 down from its August high of 86.7% (readjusted number), to 79.2% in the CDC's latest Nowcast.
According to the UK's latest Technical Briefing, BA.5 still accounts for > 85% of UK cases, but ". . . but at least 3 (BA.2.75.X, BF.7, BQ.X) show evidence of a positive growth rate compared to BA.5".
Admittedly, testing and surveillance isn't what is was even a few months ago, and there is a greater degree of ambiguity in the numbers. Nevertheless, the pattern has been with COVID that eventually, dominant strains run out of steam and are replaced by something `new'.
How long that will take, and what (if any) changes that will make in the impact of the pandemic, are unknown.
The CDC's Friday update to their Nowcast shows BA.4.6 (at 13.6%) and a relative newcomer, BF.7 (at 4.6%) making the biggest inroads against BA.5. BA.2.75 (at 1.8%) continues to creep up slowly.
Similar to what we've seen reported from Denmark this week (see SSI Reports Fall Increase In COVID Cases & Hospital Admissions), the number of COVID hospitalizations in the UK has gone up over the past month (see graph below), roughly doubling since mid-September.
The UK's Technical Briefing #46 provides the following summary and risk assessment of their COVID surveillance.
Summary and situational risk assessment
1. The genomic surveillance dataset is currently challenging to interpret due to continued changes in testing as well as proliferation of similar variants.
2. A number of new variants have begun to circulate in the United Kingdom (UK) in recent weeks. The development of these additional lineages has been rapid. They have varying Omicron backbones but some convergent receptor-binding domain (RBD) mutations (notably at S:346) which are likely to produce a degree of escape from current immunity in the UK (MODERATE confidence due to predictive and laboratory data).
3. All new variants are currently at relatively low individual prevalence but at least 3 (BA.2.75.X, BF.7, BQ.X) show evidence of a positive growth rate compared to BA.5 (MODERATE confidence due to growth rates estimated by 2 methods). The magnitude of the growth advantages in some cases is in the same range as other variants which have caused increased incidence, such as other Omicron lineages (LOW confidence as early in the growth trajectory).
4. From UK data, BQ.X, BA.2.75.2 and BF.7 are the most concerning variants in terms of both growth and neutralisation data at present; there is also supportive animal model data for BA.2.75. (LOW confidence due to early and incomplete data on other variants). They will be prioritised for vaccine effectiveness assessment.
5. Overall variants may be contributing to the current increase in coronavirus (COVID-19) incidence (LOW confidence), however given the age mix and the timing of the increase in incidence compared to the variant prevalence, it is likely that other factors are contributing
6. Note is also made of small numbers of genomes from several recombinant lineages with novel spikes, but there are no current indicators of concerning growth.
While a changing COVID variant landscape was inevitable - and there are currently no signs suggesting that any of these rising variants pose a greater health threat than BA.5 (except, potentially, greater immune escape) - the current `mild' virus still claims 200-to-300 American lives every day.
With winter coming, and the potential for seeing a severe concurrent flu season, we can't assume that we are out of the woods yet.
