A new COVID-19 variant, NB.1.8.1, nicknamed “Nimbus,” is making waves globally, and it’s not just because of its catchy name. First detected in China in January 2025, this Omicron subvariant has spread to at least 22 countries, including the United States, where it accounts for an estimated 37% of cases as of early June. What’s grabbing attention, though, is a particularly vivid symptom some patients are reporting: a sore throat so severe it feels like swallowing razor blades. Let’s dive into what we know about NB.1.8.1, its symptoms, and how to stay safe.
What Is NB.1.8.1?
NB.1.8.1 is a descendant of the Omicron variant, specifically derived from the recombinant XVD.1.5.1 lineage. According to the World Health Organization (WHO), it’s classified as a “variant under monitoring” due to its rapid spread, jumping from 2.5% to 10.7% of global COVID-19 samples between April and May 2025. In the U.S., it’s the second most dominant strain, trailing just behind LP.8.1. The variant’s nickname, “Nimbus,” reflects its cloudy, elusive nature and conveniently nods to its NB lineage, making it easier for the public to track.
The variant’s spread is likely due to mutations in its spike protein, which allow it to bind more effectively to ACE2 receptors on human cells. This makes NB.1.8.1 more transmissible than some of its predecessors, though experts, including Dr. Peter Chin-Hong from the University of California, San Francisco, note it doesn’t appear to cause more severe illness overall. Hospitalization rates remain stable, and the WHO assesses its global public health risk as low.
The “Razor Blade Throat” Symptom
The hallmark of NB.1.8.1 in the public eye is the “razor blade throat,” a term patients have used to describe an excruciating sore throat. Social media platforms like Reddit and Weibo are filled with accounts of throat pain so intense it feels like “swallowing shards of glass.” One user described it as “brutal,” noting difficulty speaking, eating, or staying hydrated. While sore throats are a common COVID-19 symptom—reported by about 70% of patients—this variant’s version seems particularly severe for some.
However, experts caution that “razor blade throat” isn’t unique to NB.1.8.1. Dr. Aaron Glatt from Mount Sinai South Nassau explains that severe sore throats can occur with various viral infections, including other COVID-19 strains, as well as bacterial infections like strep throat. The inflammation of the oropharynx, caused by the virus directly infecting throat cells, can lead to this intense pain. Testing is crucial to distinguish between COVID-19 and other causes, as strep throat, for instance, requires antibiotics to prevent complications.
Other Symptoms and Precautions
Beyond the dramatic throat pain, NB.1.8.1 presents symptoms typical of other Omicron variants: fever, cough, fatigue, muscle aches, congestion, headache, nausea, and loss of taste or smell. The CDC hasn’t identified any symptoms exclusive to this variant, but its transmissibility makes vigilance key, especially for vulnerable groups like the elderly or immunocompromised.
The good news? Current COVID-19 vaccines, particularly the 2024-2025 formulations, are expected to remain effective against NB.1.8.1, reducing the risk of severe outcomes. The CDC recommends vaccinations for everyone over six months, especially high-risk individuals. However, recent changes under U.S. Health Secretary Robert F. Kennedy Jr. have sparked controversy by removing routine vaccine recommendations for healthy children and pregnant women, a move criticized by public health experts.
To manage “razor blade throat,” experts suggest over-the-counter remedies like ibuprofen, throat lozenges, warm saltwater gargles, and hydration with warm teas or broths. If symptoms persist or worsen, or if you experience difficulty breathing or high fever, consult a healthcare provider to rule out other causes.
Staying Safe Amid the Surge
With NB.1.8.1 driving a potential summer surge, especially in regions like California where it may account for 55% of cases, precautions remain familiar: wear masks in crowded indoor spaces, practice good hand hygiene, and maintain physical distance from symptomatic individuals. Wastewater surveillance in areas like Los Angeles and Santa Clara County shows rising viral levels, signaling increased community transmission.
While NB.1.8.1 doesn’t appear to be a game-changer in terms of severity, its rapid spread and painful symptoms are a reminder that COVID-19 remains a persistent threat. Stay informed, keep vaccinations up to date (if you decide they are for you), and don’t ignore a sore throat—it might just be more than a scratchy nuisance.
Sources: ABC News, Healthline, WHO, CDC
