Latest Covid Wave Driven By Eris, But Pirola Is Waiting In The Wings

Since 2020, there’s been an ever-evolving Covid-19 landscape as new (sub)variants of the coronavirus emerged over time. Several weeks ago, the U.K.’s Health Security Agency announced the identification of EG.5, an Omicron sub-variant of the coronavirus or SARS-Co-V-2. The sub-variant has since been named Eris.

Eris is now the dominant sub-variant in the U.S., surpassing XBB.1.16, “Arcturus”, according to data from the Centers for Disease Control and Prevention. Eris’s novel spike protein mutations may facilitate ease of transmission. But just as the world is getting used to seeing Eris gain steam, BA.2.86, dubbed Pirola, may be hot on its heels as the next concerning sub-variant of Omicron. Despite only a small number of officially confirmed cases worldwide, Pirola is garnering attention because it is likely more immune-evasive and therefore better able to overcome people’s built-up immunities.

About 10 days ago, the World Health Organization designated EG.5 or Eris as a “variant of interest” which countries ought to monitor. It is a descendant of the Omicron sub-variant XBB.1.9.2 and has one conspicuous mutation which helps it evade antibodies developed by the immune system in response to earlier infections and vaccines.

Though Eris is not thought to cause more severe symptoms than prior Omicron sub-variants, it’s too early to definitively declare that it is less severe or more infectious.

Even if Eris is deemed no more severe, it can still cause misery. And in vulnerable populations, such as the elderly and immunocompromised, there’s the distinct possibility of severe illness.

Possible symptoms related to Eris run the gamut from fever to fatigue, muscle and chest pain, congestion, cough, headache, nausea, diarrhea, vomiting, sore throat and notably, a loss of taste or smell—like several early coronavirus variants.

Just as Eris hits its stride, the world may need to prepare itself for the arrival of BA.2.86, nicknamed Pirola, as the next sub-variant of interest.

Throughout the Covid-19 pandemic, the evolutionary biologist T. Ryan Gregory has provided in-depth analyses of emerging variants and sub-variants. Gregory tracks these developments closely. He says that it’s not certain Pirola will take off and outcompete other sub-variants. But Pirola’s 30 mutations that differ from a formerly dominant sub-variant XBB.1.5 (Kraken) make it a highly mutated virus, which could mean more immune escape properties which in turn could lead to more transmissibility.

Though Pirola has established international transmission with the potential for rapid growth, based on the relatively few confirmed, genome-sequenced cases thus far, the initial risk assessment posted by the UKHSA says it’s too early to make a call on its transmissibility, severity, or how likely it is to evade the protection offered by vaccines.

Nevertheless, Pirola has been designated a “variant under monitoring” by the WHO, amid concern it could represent a big enough evolutionary leap to drive new waves of Covid-19. Pirola appears to have descended from the Omicron BA.2 sub-lineage, which generated surges of the virus globally in 2022.

There is more population immunity now than there was in 2020 at the outset of the pandemic or even late 2021 when Omicron first hit. This is due to a combination of past infections and vaccinations. However, such immunity doesn’t necessarily prevent transmission. In fact, repeated infections have become par for the course. This increases the risks of a person suffering from long Covid. Moreover, more population-wide infection implies that there is an increasing amount of viral replication which can give rise to more novel (sub)variants.

Updated vaccines are coming in September. They will target XBB.1.5 (Kraken) and should work to prevent severe illness from some of the more recent XBBs, such as Eris. But it’s unclear whether the vaccines will be effective against Pirola.

The perpetually mutating coronavirus can turn vaccine development into a game of cat and mouse. Here, the vaccines are often one step behind the coronavirus.

This doesn’t mean the vaccine is of no benefit. It still confers a high degree of protection against developing severe illness.

Nonetheless, for vulnerable people and those living with or in close proximity to them the optimal strategy against Pirola or any other sub-variant is vaccination coupled with preventive measures: Reduce transmission using (K)N95 masks, indoor air ventilation and filtration and avoidance of high risk exposure settings.

As former Surgeon General Jerome Adams wrote, “taking such recommended precautions against an infectious disease that has hospitalized and killed millions is normal.” It shouldn’t be construed as an overreaction, particularly in light of the fact that before Covid-19 a surge in any communicable disease prompted public health authorities to alert the public, recommend steps to prevent transmission and, if possible, get vaccinated.

At a time when the Omicron sub-variant Eris has been driving case growth and hospitalization rates in the U.S. and Pirola may be waiting in the wings, it’s crucial that the public stays informed. While unvaccinated individuals remain at higher risk for severe illness, public health officials around the globe recommend boosters for at-risk sub-populations.