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A newly identified Covid-19 variant, named NB.1.8.1, has now been detected in the UK and placed on the World Health Organization’s (WHO) watchlist. This variant is one of six currently under global surveillance due to a sharp rise in infections.
The variant has grown to represent over 10% of global Covid cases, sparking concerns it may become the dominant strain by next winter. According to a WHO report, while it may spread more easily than previous strains, there’s no current evidence that it causes more severe illness.
Global Spread of NB.1.8.1
NB.1.8.1 was first identified on January 21, 2025, and has since spread rapidly. By late April, it accounted for 10.7% of all sequenced cases worldwide—up from just 2.5% a month earlier. The variant has been found in 22 countries, including Australia, China, the US, Hong Kong, and Thailand.
In the UK, Northern Ireland and Wales have both confirmed cases. Northern Ireland has identified at least seven cases, and a small number have also been sequenced in Wales.
Despite the global rise, the overall health risk is considered low, although certain regions have seen increasing hospital admissions.
Transmissibility and Symptoms
WHO data suggests NB.1.8.1 may spread more effectively due to mutations that enhance its binding to human cell receptors. However, there is no indication it causes more severe symptoms compared to other Omicron-related strains.
Symptoms appear to remain largely consistent with previous versions of Covid-19. These include:
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High temperature or chills
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Persistent cough
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Loss or change in smell or taste
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Shortness of breath
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Fatigue
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Headache or muscle aches
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Sore throat or congestion
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Nausea or appetite loss
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Diarrhoea
Vaccine Effectiveness
Current Covid vaccines are expected to remain effective against NB.1.8.1, particularly in preventing severe illness. WHO advises continued vaccination, especially during spring and winter campaigns, as part of ongoing public health efforts.
Experts, including Professor Francois Balloux from UCL, believe the variant is “well-adapted” and capable of partially evading immunity from past infections and vaccinations—yet it doesn't currently pose a significantly greater health threat.
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