US COVID markers continue upward trend as newer XBB variant proportions grow

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All of the indicators that the Centers for Disease Control and Prevention (CDC) uses to track COVID-19 activity increased in recent week, amid growing proportions of newer XBB variants, especially EG.5.

In other COVID developments, initial antibody experiments with the closely watched and highly mutated BA.2.86 variant suggest that it has the capacity to evade XBB-induced antibodies but may not be as infective as viruses that are currently dominant.

Activity continues to rise, especially in South

COVID hospitalizations have now been slowly rising for 8 straight weeks, starting from a very low level.

For the week ending August 19, admissions increased 18.8% compared to the previous week, with admission rates low across much of the country and higher in southeastern states. A few counties in Texas and at the Mississippi-Alabama border are listed as having high activity on the CDC's COVID data map.

Deaths from COVID rose 17.6% last week and make up 2% of the nation's deaths.

Among other indicators, emergency department visits rose 19.4% from the previous week and are highest in the South and Southeast, especially Alabama, which is in the substantial category. Many of the other states in the region are listed as moderate for hospitalizations.

Test positivity also continues to creep upward, rising 1.4% last week, putting the national positivity level at 14.9%. The level is highest—just over 20%—in Texas and surrounding states.

Biobot's wastewater tracking shows a continuation of a gradual rise since about the middle of June, with levels highest in the South and West.

XBB variant proportions continue shift

The CDC today posted its latest estimate of variant proportions, which shows continued growth of newer XBB viruses.

At 21.5%, EG.5 makes up the greatest proportion, up from 18.6% in the last update 2 weeks ago. Other variants that showed growth were FL.1.5.1, XBB.1.16 and its offshoots, and HV.1, which appears on the CDC's list for the first time. HV.1 is part of the XBB.1.9.2 lineage.

Some of the newer variants have spike mutations, including F456L, that allow the viruses to bind more tightly to ACE2 cell receptors.

BA.2.86 doesn't appear in the variant proportions, because its numbers are very low. So far, only a few states have detected the virus in patient samples or wastewater.

Mixed picture from neutralization tests for BA.2.86

Investigations are under way to gauge the immune escape and other properties of the heavily mutated BA.2.86 variant, and yesterday Yunlong Richard Cao, PhD, who heads a lab at Peking University in Beijing, on Twitter reported initial findings from experiments involving pseudovirus neutralization assays and antigenic cartography.

The team found that BA.2.86 can significantly escape antibodies from XBB infection or vaccination, but that infectivity may be lower than XBB.1.5 and EG.5, a factor that Cao said may affect transmission. "The updated vaccine's efficacy against BA.2.86 should be closely monitored; however, BA.2.86 may not prevail very fast due to its lower infectivity," he wrote.

Kristian Andersen, PhD, with the department of immunology and microbiology at Scripps Research Institute, in Twitter comments on the Cao lab's findings, said BA.2.86 and its sublineages will likely become dominant in the months ahead, but a big question is whether it can regain the transmissibility of previous variants.

Also commenting on Cao lab's results, Tulio de Oliveira, PhD, who directs South Africa's Centre for Epidemic Response and Innovation, said more lab results from lab assays should be made public in the next few days.

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