“New Covid Variant ‘Nimbus’ Under WHO Watch: Here’s What You Need to Know”

A newly emerging COVID-19 variant, NB.1.8.1, informally known as Nimbus, is gaining global attention due to its rapid spread and unusual symptom described as “razor blade throat”. First identified in January 2025, this Omicron descendant has been flagged by the World Health Organization (WHO) as one of six variants under close observation. As infections rise across the US, UK, and parts of Asia, experts are monitoring its transmissibility, severity, and impact on public health systems.

Why in News?

The WHO has listed NB.1.8.1 (Nimbus) as a variant under monitoring, due to its fast-growing prevalence. Described by some patients as causing extremely painful sore throats, the variant has triggered renewed caution globally. India has reported COVID-related deaths, but not specific cases of Nimbus yet, as per current sequencing data. Public concern is growing due to viral descriptions of “razor blade throat” and a new subvariant XFG (Stratus) circulating alongside Nimbus.

Key Facts

• Variant Name: NB.1.8.1 (Nimbus)
• Lineage: Descendant of Omicron
• First Identified: January 2025
• Symptom Highlight: “Razor blade throat” – intense sore throat
• Detected In: 13 US states, UK, China, Singapore, Thailand, India (monitoring stage)
• Global Presence: Detected in 22 countries, accounting for 10.7% of sequenced cases (April 21–27, 2025)

Symptoms (Similar to Omicron)

• Cough, fever, headache, fatigue, congestion
• Muscle aches, nausea or vomiting
• Loss of taste/smell
• Severe sore throat in some cases (“razor blade throat”)

What Is “Razor Blade Throat”?

• Not a medical term, but a popular description of severe throat pain
• Feels like glass shards in the throat
• Common in other viral and bacterial infections as well

Is Nimbus Dangerous?

• WHO risk level: Low
• Causes mild to moderate illness
• No major surge in hospitalizations or deaths reported yet
• Current vaccines remain effective

India’s Situation

• Daily cases: 100–200, stable as per Dr Arup Halder
• No confirmed Nimbus cases, but authorities are cautious
• Rise in respiratory illnesses due to H3N2 and adenovirus
• ICMR urges testing for severe symptoms, especially in vulnerable groups

Other Variant – XFG (Stratus)

• Another fast-spreading Omicron subvariant
• Not currently under WHO monitoring
• Fewer sequenced cases compared to Nimbus