- WHO monitors a rise in global Covid-19 cases linked to the Nimbus variant NB.1.8.1.
- Nimbus has been detected in at least 13 US states, including California and New York.
- UK reports a 10% increase in hospital admissions, totaling 947 patients in late May.
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.
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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."
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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.
NDTV spoke to Dr Sanjay Rai from AIIMS in Delhi who said razor blade throat happens even in bacterial as well as viral infection. He advised people to exercise caution by saying, "People who already have cough, cold and other diseases can wear a mask to make it spread less but no evidence that precautionary measures have stopped variant."
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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."
Dr Rai also called Nimbus a "mild variant". "India is in a comfortable position. Countries where the cases have increased due to this variant, the death reported haven't seen spike," he added.
Another Variant Spreading
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.
Dr Rai, meanwhile, said, "Immunity of Indians is stronger than other vaccinated countries also be it from our vaccine or natural immunity after second wave."
