New SARS-CoV-2 Variants XFG, XFC and NB.1.8.1 Likely to lead Summer COVID-19 Surge across the United States
Nikhil Prasad Fact checked by:Thailand Medical News Team May 16, 2025 10 hours, 11 minutes ago
U.S. Medical News: As of mid-May 2025, the United States is witnessing a shifting landscape of SARS-CoV-2 variants, with several subvariants of the Omicron lineage dominating circulation. According to recent data, the prevalence of these variants highlights the ongoing challenges in tracking and managing COVID-19, especially as new recombinants like XFC and XFG emerge and grow rapidly across the country.
New SARS-CoV-2 Variants XFG, XFC and NB.1.8.1 Likely to lead Summer COVID-19 Surge across the United States
This
U.S. Medical News report draws on insights from infectious disease experts and genomic surveillance data, including a notable online thread on X which compares the growth trajectories of XFC and XFG (both classified under Nextclade).
https://x.com/xz_keg/status/1922928972448301545
The data, spanning from early March to May 2025, shows XFC—a recombinant of LP.8.1.1 and LF.7—steadily climbing, reaching approximately 5% of cases nationwide by mid-May. Meanwhile, XFG, another LF.7/LP.8.1 recombinant, has also shown significant growth, though its trajectory appears more volatile. Currently about 9 percent of all cases are caused by this new variant.
Experts note that XFC’s rise has been particularly pronounced in states with larger sequencing delays, meaning its spread may have gone unnoticed until recently. Both XFC and XFG variants share similar donors and breakpoints but differ in their origins and specific mutations, with XFC lacking the S:K444R mutation present in XFG.
Adding to the complexity, the dominant variant nationwide remains LP.8.1, accounting for 40% of cases. This subvariant, alongside others like XEC (4% of cases), MC.1.10.1, LB.1.3.1, and LF.7, underscores the diversity of Omicron subvariants still circulating.
Additionally, NB.1.8.1 has emerged as another variant of note in the U.S., though its prevalence remains lower compared to XFG.
The rapid rise of recombinants like XFC, which likely emerged in the Philippines and has been detected in regions like Ethiopia, Minnesota, Delaware, Quebec, Alberta, and New Zealand, raises concerns about their potential to outcompete other variants. A GitHub issue (#2323) on SARS-CoV-2 lineage proposals highlights XFC’s specific mutations, such as Spike: H207Y and ORF1a: S1515F, which may confer a slight edge over LP.8.1.1 in certain regions.
https://github.com/sars-cov-2-variants/lineage-proposals/issues/2323
The World Health Organization emphasizes the importance of global surveillance to monitor such variants of interest (VOIs) and assess their public health risks in a timely manner.
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