KKN Gurugram Desk | The world is once again on high alert as a new COVID-19 sub-variant, NB.1.8.1, also referred to as “Nimbus”, is making headlines due to its rapid spread and unusual symptoms. While initially detected in China, the variant is now gaining ground in the United States, prompting concerns from global health authorities including the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC).

Health experts have raised alarms over the variant’s unique throat-related symptoms, its rapid transmissibility, and the possibility that it may soon account for one-third of global COVID-19 cases.

What Is the NB.1.8.1 (Nimbus) Variant?

The NB.1.8.1 strain is a newly emerging sub-variant within the Omicron family, which continues to evolve and adapt more than four years into the global pandemic. Nicknamed “Nimbus” by researchers and some health professionals, this variant has become notable not just for its speed of transmission, but for the intensity of symptoms reported by infected individuals.

The most striking and widely discussed symptom of the Nimbus variant is what some patients describe as a “razor blade throat”—an intense, sharp, and persistent throat pain that many say feels like swallowing shards of glass.

New COVID Variant 2025: Symptoms of NB.1.8.1

According to reports emerging from the U.S. and other affected countries, the symptoms of the NB.1.8.1 (Nimbus) variant include:

• Severe sore throat (described as razor blade throat)

• Nasal congestion or runny nose

• Persistent fatigue

• Mild to moderate fever

• Body aches and muscle pain

• Diarrhea

• Dry cough

These symptoms are similar in some respects to earlier Omicron variants, but the severity of the throat pain and its early onset have set NB.1.8.1 apart, leading to increased discomfort and hospital visits even in otherwise mild cases.

CDC: Variant Responsible for 37% of U.S. COVID Cases in Early June

According to the U.S. CDC, the NB.1.8.1 variant accounted for approximately 37% of COVID-19 cases in the two-week period ending June 7, 2025. This makes it one of the most dominant strains currently circulating in the U.S., surpassing several other Omicron sub-lineages.

Health experts believe that if the current trend continues, NB.1.8.1 could soon become the globally dominant strain, potentially responsible for over one-third of all new COVID-19 infections worldwide.

No Confirmed Cases in India Yet—but Monitoring Is Ongoing

As of now, no confirmed cases of the NB.1.8.1 variant have been detected in India, according to the Indian Council of Medical Research (ICMR) and the National Institute of Virology (NIV). However, Indian health authorities are actively monitoring the situation and conducting genome sequencing of recent COVID-positive samples to track emerging variants.

Speaking to the media, Dr. Naveen Kumar, Director of the NIV, Pune, confirmed that four sub-lineages of Omicron—LF.7, XFG, JN.1.16, and NB.1.8.1—have been isolated in India as part of the country’s enhanced genomic surveillance strategy.

He added that the current focus is on assessing the vaccine effectiveness against these variants and ensuring that public health responses are proactive rather than reactive.

Why Is the NB.1.8.1 Variant So Concerning?

Public health authorities are concerned about the Nimbus variant for several reasons:

1. High Transmissibility: The variant appears to spread faster than previous sub-variants, potentially contributing to localized surges in case numbers.

2. Unusual Symptom Profile: The razor blade throat symptom is causing significant discomfort and anxiety among patients, even in otherwise mild cases.

3. Immune Escape Potential: Early studies suggest the variant might exhibit partial escape from vaccine-induced immunity, although more data is needed.

4. Rapid Global Spread: From China to the United States and parts of Europe, the variant is quickly becoming geographically widespread.

While hospitalization and mortality rates linked specifically to NB.1.8.1 remain relatively low, the variant’s disruptive symptoms and rapid transmission have the potential to strain healthcare systems if not contained early.

India’s Current COVID-19 Situation: A Cautious Outlook

India is already witnessing a mild but noticeable rise in COVID-19 cases since mid-April 2025. The cause appears to be a combination of Omicron sub-variants, including NB.1.8.1, although its presence in India is still under verification.

Health experts are advising the public to:

• Resume mask-wearing in crowded or poorly ventilated areas

• Follow hand hygiene and social distancing where possible

• Stay updated on vaccination and booster recommendations

• Avoid panic and rely on credible government advisories for information

Dr. Naveen Kumar of NIV also mentioned that genome sequencing and variant tracking will be scaled up in the coming weeks to provide clearer insights.

What Should the Public Do?

Although new variants can sound alarming, public health officials stress that awareness, not panic, is the best response. Here are some recommended precautions in light of the NB.1.8.1 (Nimbus) variant:

• Monitor symptoms early: If you develop a sore throat, fever, or fatigue, isolate and get tested.

• Consult a doctor: Severe throat pain or breathing difficulty should be addressed immediately.

• Continue COVID-appropriate behavior: Especially in public transport, healthcare settings, and large gatherings.

• Stay updated: Follow verified sources like WHO, ICMR, and MoHFW for real-time guidance.

While much of the world has moved on from the crisis phase of the COVID-19 pandemic, the emergence of variants like NB.1.8.1 (Nimbus) reminds us that vigilance remains essential. With the virus continuing to evolve, early detection, accurate information, and responsible behavior are key to preventing another widespread surge.

India has so far avoided a major outbreak from the Nimbus variant, but the situation remains fluid and under close observation. The next few weeks will be crucial in determining whether this new sub-variant gains a foothold or is successfully contained.