The World Health Organization (WHO) has classified the EG.5 strain of the SARS-CoV-2 virus circulating in different parts of the world, including India, as a "variant of interest" but said it did not seem to pose more of a threat to public health than other strains.
EG.5 or Eris variant of SARS-CoV-2 was first reported on February 17 this year, and designated as a variant under monitoring (VUM) on July 19. In its latest risk evaluation on Wednesday, the WHO designated EG.5 and its sub-lineages as a variant of interest (VOI). Variants are broadly categorised into three categories: (1) variants of interest (2) variants of concern and (3) variants of high consequence.
According to the US National Institutes of Health (NIH), VOIs are defined as variants with specific genetic markers that have been associated with changes that may cause enhanced transmissibility or virulence, reduction in neutralisation by antibodies obtained through natural infection or vaccination. EG.5 is a descendent lineage of Omicron subvariant XBB.1.9.2. It carries an additional mutation in the spike protein, which the SARS-CoV-2 uses to enter and infect the human cells compared to the parent subvariant.
Within the EG.5 lineage, the subvariant EG.5.1 has an additional spike mutation and represents 88 per cent of the available sequences for EG.5 and its descendent lineages, the WHO said. As of August 7, 7,354 sequences of EG.5 have been submitted to GISAID, the Global Initiative on Sharing All Influenza Data, from 51 countries. The largest portion of EG.5 sequences are from China (30.6 per cent, 2,247 sequences).
The other countries with at least 100 sequences are the US, the Republic of Korea, Japan, Canada, Australia, Singapore, the UK, France, Portugal, and Spain. In India, only one case of EG.5 has been reported so far from Pune in May this year. Globally, there has been a steady increase in the proportion of EG.5 reported. During epidemiological week 29 (July 17 to 23, 2023), the global prevalence of EG.5 was 17.4 per cent, according to WHO.
Based on the available evidence, the public health risk posed by EG.5 is evaluated as low at the global level, aligning with the risk associated with XBB.1.16 and the other currently circulating VOIs. WHO in its risk evaluation report noted that while EG.5 has shown increased prevalence, growth advantage, and immune escape properties, there have been no reported changes in disease severity to date.
While concurrent increases in the proportion of EG.5 and COVID-19 hospitalisations (lower than previous waves) have been observed in countries such as Japan and Korea, no associations have been made between these hospitalisations and EG.5. However, due to its growth advantage and immune escape characteristics, EG.5 may cause a rise in case incidence and become dominant in some countries or even globally, according to the global health body.
WHO and its Technical Advisory Group on SARS-CoV-2 Evolution (TAG-VE) continue to recommend that countries prioritise specific actions to better address uncertainties relating to antibody escape and severity of EG.5. The global health authority has advised countries to share information on the growth advantage of EG.5 and provide sequence information.
It also urged the member countries to conduct neutralisation assays using human blood samples, representative of the affected communities, and EG.5 live virus isolates. The WHO and its Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) continue to regularly assess the impact of variants on the performance of COVID-19 vaccines to inform decisions on updates to vaccine composition.
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