The Rise of Arcturus and Eris

SARS-CoV-2, the virus responsible for COVID-19, is showing no signs of disappearing. In fact, the scientific community is in broad agreement that it is likely to remain a persistent part of our global health landscape for the foreseeable future.

Just yesterday, U.S. Senator Dick Durbin tested positive for COVID-19, a third time in the last 12 months.

While new COVID-19 hospital admissions are at their lowest levels - with fewer than two people per 100,000 being admitted - and continue to decrease, SARS-CoV-2 continues to spread. Unfortunately, as hospitalizations decrease, test positivity rates have begun to rise, indicating continued community transmission (see orange curve in the plot below).

Historically, coronaviruses were relegated to the sidelines of viral research throughout the '80s and '90s. They were viewed as minor players because the common colds they caused seemed relatively insignificant on the grand scale of human health. However, in 2020, with the emergence of the novel coronavirus, SARS-CoV-2, researchers urgently revisited this earlier research for insights into immunity.

Before SARS-CoV-2 entered the scene, only four known coronaviruses circulated among humans, including the 229E strain. These coronaviruses all caused common colds. Some experts now predict that SARS-CoV-2 may eventually become the fifth human coronavirus, causing recurrent but largely unremarkable symptoms, much like the common cold caused by the 229E strain.

Since the original virus strain of SARS-COv-2 was first identified in Wuhan, China, in December 2019, a succession of variants has emerged, each with its unique characteristics. For instance, the Alpha variant, first identified in the UK in December 2020, was the initial variant of concern. The Delta variant, first identified in India in December 2020, subsequently became the dominant strain globally and was the reason of many deaths including in the vaccinated. Later, the Omicron variant, first identified in South Africa in November 2021, has spread to many countries.

In early October 2022, a new variant of Omicron emerged - the XBB variant, quickly dubbed "Gryphon" by evolutionary biologist Ryan Gregory. This variant rapidly dominated the global landscape of SARS-CoV-2. Gryphon was considered the most immune-evasive COVID variant so far, surpassing even the immune-evasiveness of the BA.5 variant, which was globally dominant last summer.

Since late 2022, the SARS-CoV-2 lineage XBB.1.5, descendent of Gryphon nicknamed “Kraken,” has been steadily increasing in the United States, ultimately becoming the dominant lineage. 

The increased transmissibility of the XBB.1.5 lineage was partly due to its profound resistance to neutralization and enhanced ACE2 usage, a result of the S protein mutation S486P. While Sotrovimab retains neutralizing activity against XBB.1 and XBB.1.5 and remains a treatment option, novel monoclonal antibodies (mAbs) to be prepared for emerging XBB.1.5 sublineages were urgently needed. 

XBB.1.16, another sublineage of the Gryphon variant, dubbed Arcturus, first appeared in early March 2023 and exhibited significant growth. By April, the World Health Organization (WHO) elevated this fast-growing sublineage to the status of a variant of interest, observing its competitive edge over the previously dominant XBB.1.5 in many regions.

In mid-July, the number of variants of interest remained at two: XBB.1.5, which is steadily declining, and XBB.1.16, which holds steady at 20.7% of sequences.

But a new variant, EG.5, a descendant of XBB.1.9.2, has been rising in global prevalence since the end of May. On July 19, 2023, the WHO added EG.5 to its list of Omicron variants under monitoring (VUM). (see CDC dashboard). EG.5, or its subvariant EG.5.1, was nicknamed "Eris" on social media.  It's full PANGO information is EG.5.1 = XBB. = (BJ.1 x BM.1.1.1).  (BA. x BA. = (B.1.1.529. x B.1.1.529.

The second most dominant variant now is FL.1.5.1 (Fornax; similar to Flip which represents S:455F+S:456L combo). At the beginning of August, this variant was the fifth most prevalent, accounting for only 7% of cases. Arcturus is the third most prevalent. 

BA.2.86 variant, known as Pirola, was first detected in late July 2023.The numbers are still very low, but it appears to be spreading. 

The future of SARS-CoV-2 remains uncertain, but one thing is clear: it will likely be a part of our lives for a long time to come, if not indefinitely. Our focus should be on continued vigilance, scientific research, and adaptive strategies to manage its evolving presence.


Senator Dick Durbin on Twitter: "Unfortunately, I tested positive for COVID-19 today. I'm disappointed to have to miss critical work on the Senate's NDAA this week in Washington. Consistent with CDC guidelines, I'll quarantine at home and follow the advice of my doctor while I work remotely." / Twitter

Sen. Dick Durbin tests positive for COVID-19 a third time -

Dick Durbin Announces He Tested Positive For COVID For Third Time In A Year (

Durbin tests positive for COVID-19 for third time in past year (

Wang Q, Iketani S, Li Z, Liu L, Guo Y, Huang Y, Bowen AD, Liu M, Wang M, Yu J, Valdez R. Alarming antibody evasion properties of rising SARS-CoV-2 BQ and XBB subvariants. Cell. 2023 Jan 19;186(2):279-86.

Hoffmann M, Arora P, Nehlmeier I, Kempf A, Cossmann A, Schulz SR, Morillas Ramos G, Manthey LA, Jäck HM, Behrens GM, Pöhlmann S. Profound neutralization evasion and augmented host cell entry are hallmarks of the fast-spreading SARS-CoV-2 lineage XBB. 1.5. Cellular & Molecular Immunology. 2023 Apr;20(4):419-22.


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