Covid rates in the UK are surging as a new strain spreads – the NB.1.8.1 variant has been detected in at least 12 cases so far in Britain
A new strain of Covid has been discovered in the UK as rates of positive tests have soared 97% since the beginning of March.
NB.1.8.1 COVID-19 variant, sometimes referred to as the Nimbus variant, has been detected in at least 12 cases so far in Britain. The UK Health Security Agency (UKHSA) said Nimbus is making up a “growing proportion” of Covid cases worldwide. The latest UKHSA data shows a 97% increase overall in the number of positive Covid tests, with 6.1% of people giving a reading for the virus on June 1 compared to just 3.21% at on March 1.
Dr Gayatri Amirthalingam, UKHSA’s deputy director, said the agency was monitoring Nimbus. She said: “UKHSA is monitoring all available data relating to SARS-CoV-2 variants in the UK and abroad, and we continue to publish our findings in our regular Flu and Covid-19 surveillance reports.
“NB.1.8.1 has been detected in small numbers in the UK to date, but international data suggests that it is growing as a proportion of all Covid-19 cases.”
People testing positive, or who are suffering symptoms of a respiratory infection, are advised to avoid contact with vulnerable people and stay at home if possible. Symptoms include a high temperature and not feeling well enough to go to work or carry out normal activities.
A statement from the UKHSA added: “The most important thing to do is to get your vaccination when it is due if you’re eligible.
“It’s normal for viruses to mutate and change, and as more data becomes available on this variant, we’ll have a better understanding of how it interacts with our immune systems and how to optimise our protection, as well as actions we can take to keep the most vulnerable safe and live our lives as normally as possible.”
The World Health Organisation (WHO) said the new Nimbus strain accounted for just over 10% of all global cases in May.
What is the new NB.1.8.1 Covid variant and where has it come from?
“The NB.1.8.1 variant, also referred to as Nimbus, is a new strain of the Covid-19 virus that has emerged due to mutations in its genetic material,” says Dr Naveed Asif, GP at The London General Practice.
It’s a sub-variant of Omicron, says Dr Chun Tang, GP at Pall Mall Medical.
“Variants like this pop up when the virus mutates, which is normal for viruses, especially ones that spread widely,” explains Tang. “NB.1.8.1 was first picked up in early 2025 and has since been detected in several countries, including the UK, China and US. It’s got some new mutations that scientists are keeping a close eye on.”