Health officials in Britain and the United States are monitoring a renewed rise in Covid-19 cases driven by two newer variants: XFB, known as Stratus, and NB.1.8.1, called Nimbus. Case rates have increased since late summer, coinciding with the start of the fall and winter respiratory season. In the UK, test positivity has risen from about 7.6% to 8.4%, with a modest rise in hospital admissions. In the US, wastewater data show moderate spread overall, with several states reporting very high viral levels.
What makes this wave stand out is its symptom profile. Many patients report a croaky voice and an intensely painful sore throat, often described as feeling like “razor blades” in the throat. Headaches, cough, fatigue, and congestion are also common. While these overlap with past waves, clinicians say the combination can feel more severe than earlier Omicron infections.
Experts are focused on these variants mainly because of how quickly they spread, not because they appear more deadly. Higher transmissibility means more people sick at the same time, which can strain healthcare systems during colder months. Wastewater surveillance is especially important, as it captures infections even when people do not test.
Genetically, Nimbus and Stratus are Omicron subvariants with mutations that help them spread efficiently. Current evidence suggests disease severity has not significantly increased, especially among vaccinated individuals.
Vaccination and boosters remain central to prevention, along with staying home when sick, masking in crowded indoor spaces, and good hygiene. While vigilance is needed, officials stress that with awareness and responsible behavior, most people remain at lower risk of severe illness than in earlier pandemic phases.
