Eta Variant of SARS-CoV-2

Overview

The Eta variant, scientifically designated as lineage B.1.525, is a variant of SARS-CoV-2 , the virus responsible for COVID-19 . This variant was initially identified in December 2020 and has since been detected in multiple countries worldwide. The Eta variant is notable for its unique genetic mutations, which distinguish it from other variants of concern and interest.

Nomenclature and Classification

The Eta variant has been referred to by several names and codes, reflecting its evolutionary lineage and the organizations tracking it:

• Lineage B.1.525: The phylogenetic classification under the Pango nomenclature system.
• VUI-21FEB-03: Previously known as VUI-202102/03, this designation was assigned by Public Health England (PHE) as a “Variant Under Investigation.”
• Other Designations: UK1188, 21D, or 20A/S:484K.

Under the simplified naming scheme proposed by the World Health Organization (WHO) , lineage B.1.525 has been labeled variant Eta.

Genetic Characteristics

Key Mutations

The Eta variant is characterized by several significant mutations in the spike protein of SARS-CoV-2, which plays a crucial role in the virus’s ability to infect human cells. Some of the notable mutations include:

• E484K Mutation: This mutation is also found in the Gamma , Zeta , and Beta variants. The E484K mutation is associated with potential immune escape, meaning it may reduce the effectiveness of antibodies generated by previous infection or vaccination.
• F888L Mutation: A unique substitution of phenylalanine (F) with leucine (L) in the S2 domain of the spike protein. This mutation is specific to the Eta variant and its implications are still under investigation.
• ΔH69/ΔV70 Deletion: This deletion involves the removal of amino acids histidine and valine at positions 69 and 70. This deletion is also present in the Alpha variant and other variants like the N439K variant (B.1.141 and B.1.258) and Y453F variant (Cluster 5 ).

Unlike the Alpha , Beta , and Gamma variants, the Eta variant does not carry the N501Y mutation, which is associated with increased transmissibility.

Epidemiology

Global Spread

As of 5 March 2021, the Eta variant had been detected in 23 countries. By 1 July 2021, the variant had spread to a broader range of countries, with varying numbers of confirmed sequences reported to GISAID , a global science initiative providing open-access to genomic data.

Countries with Confirmed Cases

The following table provides an overview of countries with confirmed cases of the Eta variant as of 27 August 2021, based on data from GISAID:

Initial Detection and Spread

The first cases of the Eta variant were detected in December 2020 in the United Kingdom and Nigeria. By 15 February 2021, the highest frequency of this variant among samples was observed in Nigeria. As of 24 February 2021, 56 cases were found in the UK. Denmark , which sequences all its COVID-19 cases, reported 113 cases of this variant from 14 January to 21 February 2021, with seven cases directly related to travel to Nigeria.

The variant has also been reported in Mayotte , an overseas department and region of France .

Scientific Research and Public Health Implications

Current Status and Risk Assessment

As of the latest updates, the Eta variant is classified as a “variant under investigation” by public health authorities. However, pending further study, it may be reclassified as a variant of concern if evidence suggests increased transmissibility, severity, or reduced effectiveness of vaccines and treatments.

Prof Ravi Gupta , from the University of Cambridge , spoke to the BBC and noted that lineage B.1.525 appears to have “significant mutations” already seen in some of the other newer variants. This observation is partly reassuring as the likely effects of these mutations are to some extent more predictable based on existing data from other variants.

Ongoing Studies

UK experts and international researchers are actively studying the Eta variant to understand its potential impact on:

• Transmissibility: Whether the variant spreads more easily than other variants.
• Severity: Whether infection with the variant leads to more severe disease.
• Immune Evasion: The extent to which the variant can evade immunity conferred by previous infection or vaccination.
• Diagnostic and Therapeutic Efficacy: The effectiveness of existing diagnostic tests, treatments, and vaccines against the variant.

Visual Representation

Genome Map of SARS-CoV-2 Eta Variant

The following image illustrates the amino acid mutations of the SARS-CoV-2 Eta variant plotted on a genome map of SARS-CoV-2, with a focus on the spike protein:

This visual representation helps in understanding the specific locations and types of mutations present in the Eta variant, which can be crucial for ongoing research and the development of targeted interventions.

Context within the COVID-19 Pandemic

The Eta variant is part of the broader landscape of variants of SARS-CoV-2 that have emerged during the COVID-19 pandemic . Understanding these variants is crucial for global public health efforts to control the spread of the virus and mitigate its impact.

Variants of Concern and Interest

The WHO and other health organizations have classified several variants based on their potential impact:

• Variants of Concern (VOC) : Variants that have been demonstrated to be more transmissible, cause more severe disease, or evade immunity. Examples include:

  • Alpha (B.1.1.7)
  • Beta (B.1.351)
  • Gamma (P.1)
  • Delta (B.1.617.2)
  • Omicron (B.1.1.529)

• Variants of Interest (VOI): Variants that have genetic changes predicted or known to affect virus characteristics such as transmissibility, disease severity, or immune escape, but with limited evidence. Examples include:

  • Epsilon (B.1.427/B.1.429)
  • Zeta (P.2)
  • Eta (B.1.525)
  • Theta (P.3)
  • Iota (B.1.526)
  • Kappa (B.1.617.1)
  • Lambda (C.37)
  • Mu (B.1.621)

Timeline and Global Response

The emergence of the Eta variant coincides with the ongoing global efforts to monitor and respond to the evolving COVID-19 pandemic . The timeline of the pandemic, responses, and the impact of various variants can be explored in detail through the following links:

• Timeline of the COVID-19 pandemic
• Responses to the COVID-19 pandemic
• Impact of the COVID-19 pandemic

Conclusion

The Eta variant of SARS-CoV-2 represents a significant area of ongoing research and public health concern. While it shares some mutations with other well-characterized variants, its unique genetic profile warrants continued surveillance and study. As the global scientific community works to understand the implications of the Eta variant, it remains crucial to adhere to public health measures, including vaccination, testing, and adherence to guidelines designed to limit the spread of COVID-19.

See Also

• COVID-19 portal
• Medicine portal
• Viruses portal
• Variants of SARS-CoV-2 : Alpha , Beta , Gamma , Delta , Epsilon , Zeta , Theta , Iota , Kappa , Lambda , Mu , Omicron