Infection from Omicron Sub-Lineages

SARS-CoV-2 continues to evolve since its appearance. Over the past two years, several variations of concern (VOCs) and variations of interest (VOIs) have arisen. These designations, assigned by the World Health Organization, reflect their evaluated potential to lead to new waves of increased circulation and subsequent impact.

Among the variants of concern, Omicron stands as the most distinctive variant. Since its initial appearance, Omicron viruses have undergone ongoing genetic and antigenic evolution, resulting in a growing array of sub-lineages. These viruses show a close genetic relationship with other globally prevalent variants.

Since February 2022, the Omicron viruses have made up more than 98% of the sequences that are accessible to the public. They form the genetic foundation from which new variants of SARS-CoV-2 have arisen. The previous system classified all Omicron sub lineages as part of the Omicron VOC.

On 15 March 2023, the World Health Organization (WHO) variant tracking system has considered the classification of Omicron sub lineages independently as variants under monitoring (VUMs), VOIs, or VOCs.¹

The pandemic of COVID-19 which plagued the mankind has receded; but the Corona virus has not disappeared. The condition has waned with successful vaccinations and better social management.

COVID-19 is now an established and ongoing health issue. The new EG.5 (that includes a similar EG.5.1 strain) or ‘Eris’ (nick name) Covid strain is spreading across the world. This version of the virus has undergone mutations, leading to its distinct features.

This sub variant descendant of Omicron is becoming a dominant strain in many countries of the World. WHO has classified it as ‘variant of interest’. It poses a minimal global public health risk, aligning with the current status of other circulating variants.

Eris infection spreads rapidly due to its immune escaping properties. The variant does not pose a serious threat to public health when compared to previous strains.²

Eris infection presents symptoms similar to those caused by earlier variants of Omicron that includes, fever, persistent dry cough, shortness of breath, sore throat, fatigue, body ache, myalgia, running nose, alteration in taste and smell. The infection is not associated with severe manifestations. There is no increased risk of hospitalization or death compared to other variants.

The SARS CoV-2 variant, EG.5.1 (descendent of the XBB. 1.9.2.5.1) is a sub-lineage of the Omicron variant XBB.1.9.2. The strain possesses two additional spike mutations compared to its parent strain and shares a spike amino acid profile with XBB.1.5. They have been identified in China, US, South Korea, Japan, Canada, Australia, Singapore, UK, France, Portugal and Spain. EG.5.1 strain was first recognized on March 24, 2023. Only one case has been reported in India on May 29, 2023 at Pune, Maharashtra during genome-sequencing of Covid-positive RT-PCR samples.³

In accordance with other variants presently circulating, the World Health Organization (WHO) has affirmed that the new strain poses a limited public health risk to humanity. EG.5 exhibits immune escape properties.

Vaccine reformulations have been able to target at XBB variants descended from Omicron. The vaccines are able to induce functional immune responses to XBB sub variants, and offer better protection to EG.5.

There is no evidence to indicate that EG.5 can spread more easily and it has a low risk to public health in comparison to other Omicron descendants. It is less invasive. Thus, it is unlikely to cause more severe disease. Currently available treatment modalities such as social distancing, practice of hand hygiene and face mask, and vaccines appear to be effective against this variant.

Due to seasonal fluctuations, the condition may be confused with common cold or influenza in the absence of testing. Since COVID-19 has not totally vanished, one need not panic with emergence of variant strains.

WHO has urged to maintain surveillance and reporting, variant tracking and early clinical care. Regular monitoring of the variants of Corona virus must be maintained.

Though the pandemic of COVID-19 is no longer a threat, the spread of COVID-19 does not appear to have slowed down. India has witnessed multiple waves in the last three years. The ever evolving SARS-CoV-19 virus has made its appearance in the form of new variants of Omicron such as BA2.86. As the mass vaccination program has boosted the immunity of people, new variants do not pose a threat. Apart from EG.5, other most common sub variants in circulation are Omicron XBB descendent, FL.1.5.1, and XBB.1.16 (Arcturus). According to WHO, globally EG.5 and XBB.1.16 are the most prevalent COVID-19 strains and it has been found that they account for 21% of sequences worldwide.⁴

A new variant that is genetically different from Omicron, -BA 2.86 (nicknamed ‘Pirola’) was first noted in Israeal in late July as a descendent from the Omicron BA,2 sub lineage. Then it made its appearance in the US, Denmark, and UK. Six cases have been reported worldwide by 20th August 2023, according to global virus database. BA.2.86 has a large number of mutations compared to other circulating COVID variants.⁵

The WHO has named this COVID-19 variant as a ‘variant under monitoring’ (VUM) since it carries a large number of mutants. This new sub-variant of the Omicron is associated with many changes in antigenic and spike structures that can increase the affinity towards ACE 2 receptors and escape immunity. It is too early and difficult to label whether the variant is more infectious or dangerous than Eris variant, as the number of cases reported are very few. The symptoms of the variant are similar to that of flu.

BA.2.86 shares about 30 of the same spike mutations facilitating its attachment more easily to receptors in the cells, thereby exhibiting an increased ability to cause infection. The variant has capacity to spread. This new variant is not yet a cause for alarm. New strains are detected only by testing and sequencing.

The same pandemic protocols that were carried out to prevent the spread of disease will be effective. Masking, social distancing, hand hygiene, testing, avoiding sick people, and vaccinations are critical in its control.

Conflict of interest

None