Razor Blade Throat’ Symptom Linked to New COVID Variant NB.1.8.1 Rising Across the U.S.

Introduction

In the summer of 2025, as the world adjusts to post-pandemic norms, a new COVID-19 variant has entered the scene: NB.1.8.1, nicknamed “Nimbus” or Razor blade throat covid variant Although not currently classified as a Variant of Concern, this subvariant has raised eyebrows among scientists and public health experts due to its rapid spread, unusual symptoms, and potential immune evasion capabilities.

As of June 2025, Nimbus has become the second-most common COVID-19 strain in the United States, with detection in multiple countries across Asia, Europe, and North America. With vaccination efforts still ongoing and respiratory infections seeing a seasonal uptick, understanding this variant is crucial for both healthcare providers and the general public.

In this article, we explore everything you need to know about Nimbus: its origin, symptoms, impact in the USA, transmissibility, severity, vaccine efficacy, and what health agencies like the CDC and WHO are recommending.

What is NB.1.8.1 (“Nimbus”)?

NB.1.8.1, known by its informal name “Nimbus,” is a recombinant subvariant of the Omicron lineage, tracing its genetic roots to earlier lineages such as JN.1 and XDV. It features unique spike protein mutations that scientists believe may give it advantages in transmission and immune escape.

It was first detected globally in early 2025, and within months, it began spreading rapidly across continents. Due to its rising presence, the World Health Organization (WHO) has placed Nimbus under the “Variant Under Monitoring” category—an early warning designation for potentially problematic strains.

Global Spread and U.S. Situation

International Reach

By June 2025, NB.1.8.1 had been identified in over 20 countries, including:

• United Kingdom
• Singapore
• Thailand
• China
• India
• United States

In many of these countries, public health agencies noticed a gradual but steady increase in COVID-19 test positivity rates. Several Asian nations experienced brief spikes in respiratory illness cases during late spring, with NB.1.8.1 contributing significantly to that rise. Health experts are closely watching international travel trends as they could facilitate the variant’s cross-border transmission.

Despite its increasing footprint, no countries have imposed travel bans or lockdowns, as the variant has not shown signs of causing widespread severe illness or overwhelming hospitals.

U.S. Trends and Numbers

In the United States, the CDC reported that Nimbus made up approximately 37% of all new COVID cases by early June 2025. It is now:

• The second-most prevalent variant in the country.
• Detected in at least 14 U.S. states, with concentrations in New York, New Jersey, Massachusetts, California, and other densely populated areas.
• Coinciding with a slight increase in emergency room visits, though hospitalizations and deaths have not shown significant surges.

Public health authorities note that urban areas with high commuter activity and summer tourism may see faster spread. However, the overall risk remains manageable due to widespread vaccination, hybrid immunity, and the generally milder nature of recent Omicron subvariants.

Despite its growth, public health data shows that COVID-19 activity is still relatively low across most of the country, except for isolated upticks.

What Makes Nimbus Different?

While many symptoms overlap with prior Omicron subvariants, NB.1.8.1 is being noted for causing a more severe sore throat, described by some patients as “razor blade throat.” It’s said to feel like swallowing broken glass—more intense than the standard COVID-related sore throat.

Common Reported Symptoms:

• Extremely painful sore throat
• Mild fever or chills
• Body aches
• Dry cough
• Fatigue
• Headache
• Runny or congested nose
• Less frequent loss of taste/smell (as seen in earlier variants)

Doctors emphasize that this sore throat should not be dismissed as a common cold or strep infection. Testing is highly recommended if symptoms arise.

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Is Nimbus More Dangerous?

Severity

So far, there is no evidence that NB.1.8.1 causes more severe illness than other Omicron subvariants. Data from the U.S. and other countries show:

• Stable hospitalization rates
• No spike in COVID-related deaths
• Normal functioning of healthcare systems

Experts suggest that although it may spread more easily or evade immunity slightly better, it doesn’t appear to be more virulent (dangerous) than previous strains.

Are Vaccines Effective Against Nimbus?

CDC and Expert Analysis

Yes—current vaccines still offer strong protection, particularly against severe disease, hospitalization, and death. The 2024–2025 updated COVID-19 vaccines (Pfizer, Moderna, and Novavax) were designed to target JN.1-derived strains, which share similar spike mutations with NB.1.8.1.

While the variant might slightly reduce the neutralizing antibody response, real-world data shows that vaccines continue to be:

• Highly effective in preventing severe outcomes
• Useful in reducing symptom severity
• Important for slowing community transmission

The CDC continues to recommend booster shots for:

• Adults over age 65
• People with underlying conditions
• Immunocompromised individuals
• Healthcare workers and long-term care residents

Do Treatments Still Work?

Yes. Current antiviral medications like Paxlovid (nirmatrelvir/ritonavir) remain effective against NB.1.8.1. So far, no evidence suggests the variant is resistant to available oral antivirals or monoclonal antibodies.

Doctors advise starting treatment within 5 days of symptom onset for best results—especially in high-risk patients.

What Can You Do to Stay Safe?

Even though Nimbus isn’t causing a major public health crisis yet, simple measures can help limit its spread—especially in crowded places or around vulnerable individuals.

Recommended Safety Tips:

1. Stay updated with your COVID vaccine and booster.
2. Test if symptomatic, especially with sore throat or cough.
3. Wear a mask in high-risk indoor settings like clinics or public transit.
4. Ensure good ventilation in your living and working spaces.
5. Practice good hygiene: frequent handwashing and sanitizer use.
6. Avoid close contact with people if you feel unwell.

For those in high-risk groups, these steps remain crucial, especially with potential summer surges.

What Are Health Agencies Saying?

CDC (Centers for Disease Control and Prevention):

• Currently monitoring NB.1.8.1 closely.
• Recommends staying up to date with vaccination and boosters.
• Advises continued use of personal protective measures where needed.

WHO (World Health Organization):

• Classifies Nimbus as a Variant Under Monitoring.
• States that it poses a low risk to global public health at this time.
• Emphasizes surveillance and data collection to stay ahead of possible developments.

Summary Table – NB.1.8.1 (Nimbus)

Feature	Details
Lineage	Omicron-derived (XDV > XBD > JN.1)
Nickname	Nimbus
Detected	First identified globally in early 2025
U.S. Share	~37% of cases (as of June 2025)
Symptoms Highlight	“Razor blade throat,” fatigue, cough
Vaccine Response	Vaccines remain effective
Treatment Response	Antivirals like Paxlovid still work
WHO Status	Variant Under Monitoring
CDC Guidance	Stay vaccinated, test if sick, wear masks if at risk

Final Thoughts

While NB.1.8.1 (Nimbus) is showing signs of rapid spread and some distinct symptoms, it is not currently a cause for alarm. Thanks to prior vaccination campaigns and improved awareness, most populations are better equipped than in the early days of the pandemic.

That said, it’s vital to:

• Keep an eye on symptoms
• Stay updated with boosters
• Follow health guidelines
• Avoid misinformation

Nimbus may be a reminder that COVID-19 is not gone, but with the right tools and awareness, it can be kept under control.

References & Sources

1. CDC COVID Data Tracker
2. AP News – COVID variant with “razor blade throat”
3. WHO Weekly Epidemiological Update on COVID-19
4. Houston Chronicle – Razor Blade Throat Symptoms
5. Wired – WHO monitors new COVID variant spreading in U.S. and Europe

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