Covid-19 Variant NB.1.8.1
The Covid-19 pandemic continues to evolve with new variants. The recent emergence of the NB.1.8.1 variant, also known as ‘Nimbus’, has drawn attention due to its rapid spread, particularly in China and the United States. This variant is associated with a unique symptom referred to as a ‘razor blade’ throat, characterised by severe pain during swallowing.
About the NB.1.8.1 Variant
NB.1.8.1 is a descendant of the Omicron variant. As of May 23, 2025, the World Health Organization (WHO) classified it as a SARS-CoV-2 variant under monitoring. This classification indicates that it is being tracked due to its increasing global presence. Despite its spread, WHO has assessed the additional public health risk posed by this variant as low.
Symptoms and Severity
Symptoms of the NB.1.8.1 variant are similar to those of other Covid-19 strains. Common symptoms include fever, cough, runny nose, and tiredness. The distinct ‘razor blade’ throat symptom has been reported but its uniqueness remains uncertain. Current data suggest that this variant does not cause more severe illness than other circulating variants.
Vaccination and Effectiveness
Approved Covid-19 vaccines are expected to remain effective against the NB.1.8.1 variant. Vaccination continues to provide protection against symptomatic and severe disease. Public health measures remain crucial to manage the spread of the virus.
Current Epidemiological Trends
In India, the Indian SARS-CoV-2 Genomics Consortium (INSACOG) reported a single case of NB.1.8.1 in Tamil Nadu as of April 2025. The most prevalent variant in the country remains JN.1, which accounts for over half of the samples tested. Other variants such as BA.2 and new recombinant variants are also being monitored.
Public Health Recommendations
Health officials advise ongoing vigilance. Personal protection measures such as frequent hand washing, wearing masks in crowded places, and protecting vulnerable populations are essential. Although major waves similar to those experienced in previous years are not anticipated, fluctuations in case numbers may continue.
Future Monitoring and Surveillance
Genomic surveillance has been enhanced to track the NB.1.8.1 variant and other emerging strains. The National Institute of Virology (NIV) in Pune is actively analysing variants to understand their impact on public health.
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