Everything you need to know about highly transmissible new Covid strain 'Nimbus'

Irish Daily Mirror

10-06-2025

A warning has been issued to the public over the new highly contagious 'Nimbus' strain of Covid, which has seen cases soar in Ireland.
The Nimbus variant, also known as NB.1.8.1, has been identified in 22 countries so far and by late April was responsible for approximately 10.7 per cent of global infections, up from just 2.5 per cent a month earlier.
First identified at the end of January, the variant is a descendant of the Omicron family of Covid sublineages, and has become increasingly prevalent throughout the spring in Europe, the Americas and the Western Pacific.
The new strain has been declared a "variant under monitoring" by the World Health Organization (WHO), meaning that it could change the behaviours of the virus.
Preliminary data suggest NB.1.8.1 may spread more easily and may partially evade certain immune defences, the WHO has said.
As cases of the new 'Nimbus' variant surge, we break down everything you need to know about the new Covid strain.
The new NB.1.8.1 strain has been declared a "variant under monitoring" by the World Health Organization (WHO), meaning that it could change the behaviours of the virus.
Similar to previous Omicron subvariants, NB.1.8.1 contains spike protein mutations associated with increased transmissibility. However, no evidence suggests that NB.1.8.1 causes more severe illness or significantly evades vaccine-induced or natural immunity.
NB.1.8.1 has been linked to significant increases in Covid-19 cases across several countries.
Health officials have said Nimbus' spike protein modifications could increase its transmission capacity and partially reduce the neutralising efficacy of certain antibodies generated by previous infections, both of which would contribute to its spread.
NB.1.8.1 has seen a rapid rise in Ireland in recent weeks. According to the Health Protection Surveillance Centre (HPSC), the proportion of sequenced Covid samples linked to NB.1.8.1 has jumped from just 3.7 per cent to 33.3 per cent in the last five weeks.
Lara Herrero, a virologist from Griffith University in Australia, suspects that NB.1.8.1 spreads more easily than other variants, which may be behind the recent surge in cases in Ireland and around the globe.
"Using lab-based models, researchers found NB.1.8.1 had the strongest binding affinity to the human ACE2 receptor of several variants tested, suggesting it may infect cells more efficiently than earlier strains," Dr Herrero wrote last month in The Conversation.
People in Ireland have been urged to stay home for two days if they display any signs of Covid. You should also avoid contact with other people, especially people at higher risk from Covid.
Symptoms of the new Covid strain are reported to be broadly the same as earlier versions of the virus with a painful sore throat a possible key sign of the new variant.
According to Dr Naveed Asif, GP at The London General Practice, the NB.1.8.1 variant has a distinctive symptom, a severe sore throat known as a "razor blade sensation".
Other signs of the new strain include common Covid symptoms like fever, muscle aches and congestion as well as redness in the back of the mouth and swollen neck glands.
While previous strains largely caused cold and flu like symptoms, this new variant has been linked to gastrointestinal issues in some patients - which can include nausea, vomiting, diarrhoea, bloating, constipation, abdominal pain and even heartburn.
While symptoms are generally mild to moderate, individuals with pre-existing conditions, unvaccinated persons, people with weakened immunity and older adults are at a higher risk of serious illness.
Those most vulnerable to Covid - such as the elderly, immunocompromised or those with pre-existing chronic conditions - have been urged to stay up to date with booster vaccinations to ensure they are protected against NB.1.8.1.
Health officials say that current Covid jabs remain effective against this variant and protect anyone infected from severe illness.
"Treatment for Nimbus generally aligns with that for other Covid-19 variants," says Dr Naveed Asif, GP at The London General Practice.
"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."
Despite a rise in cases, Dr. Sharad Joshi, Director & HOD, Pulmonology and Paediatric Pulmonology, Max Healthcare, has said "there's no need to panic".
"To protect ourselves and those around us, it's important to practice good respiratory hygiene," said Dr. Joshi.
"This includes wearing a mask, covering your nose and mouth when sneezing or coughing, and maintaining a safe distance where possible. It may be wise to avoid non-essential travel, large gatherings, and outings for the time being."