XFG ‘Stratus’ COVID-19 Variant Spreads Rapidly Worldwide: Latest on What We Know

The emergence of the XFG ‘Stratus’ COVID-19 variant, a recombinant of LF.7 and LP.8.1.2 lineages, has prompted significant concern due to its rapid global spread. As reported by Griffin (2025), Stratus possesses four critical mutations in its spike protein that may enhance its ability to evade immune responses, leading to a nearly two-fold reduction in antibody efficacy compared to the previous dominant variant, LP.8.1.1. This increased transmissibility has led the World Health Organization (WHO) to monitor Stratus closely as it approaches dominance over Nimbus .

Stratus variants currently account for just over 30% of COVID cases in England, up from 10% in May, according to the UK Health Security Agency (UKHSA). They are the most prevalent variants.

The World Health Organization (WHO) has said that XFG is growing rapidly globally and is thought to be slightly more infectious than previous variants.

However, experts suggest there is no need to be unduly worried. The UKHSA also says Stratus does not appear to pose any greater risk to health than other strains, and COVID cases in general are decreasing compared to recent weeks.

A “variant under monitoring” signifies a variant or subvariant which needs prioritised attention and monitoring due to characteristics that may pose an additional threat compared to other circulating variants.

XFG was one of seven variants under monitoring as of June 25. The most recent addition before XFG was NB.1.8.1 (nicknamed “Nimbus”), which the WHO declared a variant under monitoring on May 23.

Both nimbus and stratus are types of clouds.

The public health risk posed by XFG is evaluated as low at the global level, as per WHO's latest report.

However, the Lancet study has mentioned that the XFG sub-variant has the potential to spread quickly and exhibits "strong immune evasion." This allows the virus to survive and spread easily as it can evade the body's natural defences.

Is vaccination effective?

As of June 25, XFG has been designated a variant under monitoring (VUM). "Currently approved COVID-19 vaccines are expected to remain effective against this variant against symptomatic and severe disease," mentions WHO.

Recent data indicate that Stratus is particularly prevalent in Southeast Asia and accounted for approximately 30% of new COVID-19 cases in England by late June 2025 . Symptoms associated with this variant include a notably hoarse throat, which distinguishes it from earlier variants; however, current evidence suggests that it does not lead to more severe disease outcomes than those seen previously . While the WHO currently assesses the risk posed by Stratus as "low," its rapid proliferation necessitates ongoing vigilance and research into vaccine effectiveness against this emerging strain.

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Sara H

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