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17.36
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Impact LevelMedium
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Scope LevelNational
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Last Update2025-08-06
Key Impacts
Positive Impacts (9)
Negative Impacts (3)
Event Overview
The emergence of the NB.1.8.1 (Nimbus) variant as a dominant SARS-CoV-2 strain in the U.S. highlights evolving viral transmission dynamics and immune escape capabilities. Its association with atypical 'razor blade throat' symptoms underscores challenges in managing variant-driven health impacts, requiring updated clinical protocols and public health responses. The strain's rapid spread reflects ongoing pandemic adaptation pressures.
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COVID-19 NB.1.8.1 Variant (Nimbus) Becomes Dominant in U.S., Causing 'Razor Blade Throat' Symptoms
The NB.1.8.1 variant of COVID-19, also known as Nimbus, is currently the dominant strain in the United States, accounting for 43% of COVID-19 cases nationwide according to the Centers for Disease Control and Prevention (CDC). This information was discussed by Neil Maniar, director of Northeastern University's master of public health program.
The variant has been nicknamed 'razor blade throat' due to the particularly piercing sore throat it causes. Additional symptoms associated with NB.1.8.1 include runny nose, headache, fatigue, sneezing, nausea, and vomiting.
Neil Maniar explained that the painful sore throat may be caused by the variant's ability to bind more effectively to receptors in the upper airway. Maniar said, "It's probably just a function of how the SARS-CoV2 virus is able to bind more effectively to receptors in the upper airway." He added, "My understanding is that because of changes to the spike protein, this variant seems to bind better to ACE receptors which are more prevalent in the upper airway."
While NB.1.8.1 may be somewhat more transmissible due to structural changes in the virus, Maniar emphasized that it is not leading to increased hospitalizations or deaths. As of the week ending July 12, the CDC reported a COVID-19 hospitalization rate of 1 per 100,000 people, which is slightly higher than 0.7 per 100,000 reported for the week ending June 14. The CDC recorded 101 weekly COVID deaths for July 12, which is described as one of the lowest fatality counts since March 14, 2020.
The weekly COVID case positivity rate rose to 5.1% as of July 19, up from 4.2% the previous week—a 0.3 percentage point increase. Maniar noted that summer upticks in COVID cases may be due to increased travel, social gatherings, waning vaccine effectiveness, and greater transmissibility of the current variant.