Nimbus: All About New Covid Variant That Causes "Razor Blade Throat"

New Covid Variant "Nimbus": The World Health Organisation (WHO) is closely monitoring a fresh rise in global Covid-19 cases, driven largely by a new variant - Nimbus (NB.1.8.1). First identified in January 2025, this sub-variant of Omicron is now spreading rapidly across several countries.

Cases in the US and UK

According to the Global Initiative on Sharing All Influenza Data (GISAID), the NB.1.8.1 variant has been detected in at least 13 US states, including California, New York, New Jersey, and Illinois. In the UK, the UK Health Security Agency (UKHSA) reported a 10% jump in hospital admissions, with 947 patients admitted in the week ending May 31.

Also Read | Gujarat Reports Over 200 New Covid Cases In 24 Hours

Asia Sees a Surge Too

Rising infections have also been reported in parts of Asia - notably China, Singapore, Thailand, and India. In India, Covid-linked deaths crossed 100 on Monday, triggering concern among health authorities. However, cases of this variant have not been reported so far.

What is the Nimbus variant?

Designated as NB.1.8.1, the Nimbus strain is a descendant of Omicron. WHO has listed it among six variants under close observation. 

Dr Arup Halder, Consultant Pulmonologist, CK Birla Hospitals, CMRI Kolkata, told NDTV, "There are no scientifically recognised COVID-19 variants named 'Nimbus' or 'Stratus' in India or globally; these terms likely reflect unofficial labels for existing Omicron subvariants, which remain highly transmissible but cause mild illness."

Also Read | WhatsApp Is Officially Getting Ads. Here's What Changes

Symptoms: What to Watch For

The symptoms are similar to other Omicron sub-variants. As per the CDC, they include:

• Cough
• Fever
• Fatigue
• Muscle aches
• Congestion
• Headache
• Nausea or vomiting
• New loss of smell or taste

In rare cases, patients have reported a condition described as "razor blade throat".

Dr Ankita Baidya, HOD and Consultant - Infectious Diseases at Manipal Hospital Dwarka, told NDTV: "It is not necessary that they are going to give you a deadly disease."

"This time we see a sense of loss of taste and smell along with normal viral-like symptoms like fever, cough, and cold, and other flu-like symptoms like sore throat and running nose. Headache and body ache is also noted."

What Is "Razor Blade Throat"?

The term seems to be a new one, but it simply means incredibly painful sore throats, similar to cases associated with Covid-19 that surfaced before. Patients describe having a throat that feels like it's covered with shards of glass.

The term "razor blade throat" has been popularised by social media influencers and other internet users.

Also Read | What Is Driving A Surge In Covid Cases In India? Active Cases Rise To 7,121

Is Nimbus Dangerous?

The WHO, in its latest risk assessment, said the global public health risk from NB.1.8.1 remains "low". Current vaccines are expected to remain effective against both symptomatic and severe disease from this variant.

Between April 21 and 27, Nimbus accounted for 10.7% of globally sequenced cases, with 518 sequences from 22 countries.

Dr Baidya added: "Nimbus has been a fast-spreading strain since January 2025 and this variation has been noticed that though it's spreading fast among people it's not that deadlier as such, causing mild to moderate disease only."

She also flagged another variant

Besides Nimbus, another variant that has also caused concern among people is XFG, nicknamed "Stratus". It is not currently designated for monitoring by the WHO.

"Stratus is right now again under scrutiny that it's also spreading fast but if we compare the number of cases that we have seen with Nimbus strain after sequencing identified as Nimbus strain, the status cases are comparatively less," Dr Baidya said.

"But yes, these two variants are currently the most circulating variant and right now Nimbus is also under monitoring according to WHO, seeing how the pattern of disease and its pattern of spread is being studied simultaneously," she added. 

Covid cases in India

Dr Halder weighed in on India's current Covid situation, saying that it is "stable" with low cases (100-200 daily) and minimal hospitalisations. He noted that a surge in respiratory illnesses is driven by seasonal viruses (H3N2, adenovirus) amid monsoon conditions.

Warning the public, he said that people should rely solely on ICMR/Health Ministry advisories, test severe symptoms via RT-PCR to differentiate COVID from flu, and ensure high-risk groups are booster-vaccinated.