What is different about the NB.1.8.1 Covid variant?

For many of us, Covid-19 feels like a chapter we've closed – along with the days of PCR tests, mask mandates and daily case updates. But while life may feel back to normal, the virus hasn't completely vanished. In fact, new variants continue to quietly circulate.

One of the latest to appear on the radar is NB.1.8.1 – a name that you may have seen pop up in headlines and on social media feeds this week.

This newly emerging sub-variant hasn't triggered widespread concern, but it has caught the attention of scientists and health officials.

The UK Health Security Agency (UKHSA) announced this week that NB.1.8.1 has so far only been detected in small numbers within the UK, but added that international data indicates that the sub-variant is steadily accounting for a growing share of global Covid-19 cases.

We consulted some GPs to find out exactly what sets the NB.1.8.1 Covid variant apart from the rest. Is it more contagious, more immune-evasive, or simply another step in Covid's slow evolution? Here's what they know so far…

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."

How is it different from previous variants?

"NB.1.8.1 isn't too different from the Omicron variant, but it does have some tweaks to its spike protein, which might make it spread a bit more easily or slip past some of our existing immunity," says Tang. "That said, early signs suggest it doesn't seem to cause more serious illness, but of course, we're still learning more about it."

However, Nimbus does appear to be more transmissible than previous variants, with notable increases reported in India, Hong Kong, Singapore, and Thailand, notes Asif.

"Its spread has been identified in around 22 countries," says Asif. "The World Health Organization (WHO) assesses the additional risk to the global public as currently low, and existing Covid-19 vaccines are considered effective in preventing severe disease."

How is it spreading?

"It's spreading in the usual way, person to person, mainly through respiratory droplets when people cough, sneeze or even just talk closely," says Tang. "Like other variants, it can hang around in the air in poorly ventilated spaces."

What symptoms should people look out for?

"Common symptoms of the NB.1.8.1 variant include severe sore throat (described as a "razor blade sensation"), fatigue, mild cough, fever, muscle aches and congestion," says Asif. "However, symptoms can vary widely so vigilance is key."

What are the treatment options?

"Treatment for Nimbus generally aligns with that for other Covid-19 variants," says Asif. "Most individuals will recover at home with rest, hydration, and over-the-counter medications for symptom management.

"For those with severe symptoms or high-risk complications, antiviral medications or monoclonal antibody treatments may be recommended. Always consult your GP for personalised advice."

How can you avoid getting the new variant?

"Make sure everyone's up to date with their Covid-19 jabs, especially boosters," recommends Tang. "Wash your hands regularly, keep rooms well ventilated, and consider popping a mask on in busy places or if you're around people who are more vulnerable.

"If someone in the house is feeling poorly, try to keep some distance and clean shared surfaces regularly."

When should you see a GP about this?

"Seek medical advice if you experience Covid-19 symptoms, especially if they worsen or if you have underlying health conditions that increase your risk," advises Asif. "Additionally, consult your GP if you've been in close contact with someone who has tested positive for the NB.1.8.1 variant or if you have health concerns."