The dominant variant of the virus, named XFG, is better at evading immunity and could cause an increase in cases, but does not appear to be more severe than previous strains.
A seasonal uptick in COVID-19 cases across Europe and North America has drawn renewed attention to a variant known as XFG, which has been dominant worldwide over the past year. Since the emergence of the virus in 2019, several variants have succeeded one another: should we be concerned every time we hear of a new strain, or do past infections and vaccinations provide us with a reliable baseline level of protection?
Six years after the peak of the COVID-19 pandemic, “we are still in strange, uncharted territory,” says Danny Altmann of Imperial College London. “The situation isn’t as good as we had hoped—it isn’t yet like a common cold that we barely notice. But it isn’t as dire as some colleagues feared, as if we were setting the stage for the next catastrophe.”
In laboratory testing, XFG (also known as Stratus) demonstrates a superior ability to evade antibodies compared to earlier variants, which appears to be the primary reason it became dominant. For the vast majority of people, however, the immunity conferred by previous vaccinations and infections seems sufficient to prevent the disease from taking a severe form, leading researchers to urge calm and measured caution.
All variants currently in circulation descend from Omicron, the last major strain to receive a Greek letter designation, which emerged in 2021. The virus “continues to evolve,” says Ian Mellis of Columbia University in New York, giving rise to a succession of new variants that displace earlier ones and trigger waves of infection.
XFG was first identified in early 2025, and by June of that year, the World Health Organization officially designated it a variant under monitoring. It currently accounts for approximately 60 percent of sequenced global cases.
This variant arose through the exchange of genetic material between two subvariants of an Omicron strain known as JN.1, Mellis explains—likely occurring when both co-infected the same host. In early 2026, Mellis and his colleagues released test results on a range of SARS-CoV-2 viruses, including XFG and another nicknamed Nimbus, to evaluate the response of human antibodies. They found that while both bound slightly less effectively to host cells, this limitation was more than offset by a heightened ability to escape antibody neutralization compared to prior variants.
This immune evasiveness, combined with the widespread prevalence of XFG, risks exposing more individuals to noticeable symptoms and could lead to a modest rise in hospitalizations, according to Altmann. However, to date, there are no indicators of increased disease severity, nor a surge in hospital admissions or fatalities.
Winter Is Coming
Positive COVID-19 tests in the UK, % (UK Health Security Agency)
- In Italy, according to data from the Ministry of Health, confirmed COVID-19 cases recorded between October 8 and October 14 totaled 308, compared to 262 the previous week. While these figures remain low, they likely significantly underestimate actual infection rates due to low testing volume (12,848 tests performed). The positivity rate also saw a minor uptick, rising from 2.3 to 2.4 percent.
In UK hospitals, for instance, 1,638 COVID-19 cases were identified during the first week of October, up from 1,328 the previous week. However, these figures align with typical autumn projections and remain below levels recorded during the same period in 2025.
“There is currently no evidence that the new variants cause more severe illness or spread more rapidly,” explains Alexander Allen of the UK Health Security Agency, “and current vaccines have been updated to target them effectively.”
Silent Evolution
For Aris Katzourakis of the University of Oxford, assessing the immediate impact of a circulating virus can be difficult. “It takes time for an infection wave to translate into hospital admissions, and further time for those data to be publicly reported.”
Earlier this year, Leena Azhar and colleagues at the Fakeeh College for Medical Sciences in Jeddah, Saudi Arabia, reviewed available data on the XFG variant. They concluded that it exhibits a pattern of “silent” evolution—more consistent with gradual antigenic adaptations than a sudden shift toward heightened virulence.
Even though the virus is drifting further from its ancestral form and many people have not received a booster in years, “we are relying on existing population immunity,” says Altmann. “It is helping keep things manageable.”
The current situation is a far cry from the arrival of Omicron, he adds. “Omicron was so drastically different that it felt catastrophic.” Facing these latest variants, Altmann remains measured: “We are more or less right where we were.”
This does not mean a more dangerous strain could not emerge in the future—for example, if multiple mutations accumulate within an immunocompromised individual, as occurred with Omicron. As Mellis notes, “there remains a risk that a novel lineage could arise capable of driving another major wave of infections.”
Compounding the challenge, global surveillance infrastructure that could provide early warning has waned: over the past year, viral genomic sequencing has dropped off sharply. According to Altmann, governments worldwide are displaying a concerning degree of apathy regarding vaccine booster campaigns. The majority of children now entering primary school have never received a COVID-19 vaccine, the researcher points out, and the long-term public health implications remain uncertain.
The Internazionale. Translation edited by AI Assistant Gemini.
