New COVID-19 Variant "Nimbus" Spreads Globally, Raising Concerns

The COVID-19 virus is once again drawing attention, more than five years after the initial outbreak, with a new variant emerging and spreading in the UK and other countries. This new strain, named NB.1.8.1, also known as "Nimbus," now accounts for over 10 percent of global infections, with confirmed cases in England and Northern Ireland.

Experts believe that while there's no evidence the new strain causes more severe symptoms, it may infect cells more efficiently. It could also trigger gastrointestinal symptoms such as diarrhea, constipation, and nausea. Since its initial recognition in January 2025, the Omicron variant has spread to several states across the US, Australia, and Thailand, and is the most dominant variant in China and Hong Kong.

The World Health Organization has classified NB.1.8.1 as a "variant under monitoring," representing approximately 10.7 percent of all submitted sequences. The WHO noted that SARS-CoV-2 continues to evolve, with shifts in global variant dynamics between January and May 2025. Initially, XEC was the most prevalent variant, followed by KP.3.1.1. In February, XEC's circulation declined while LP.8.1 increased, becoming the most detected variant in mid-March. Since mid-April, LP.8.1's circulation has slightly decreased as NB.1.8.1 is increasingly detected.

Data from GISAID, a global database of genetic sequences, indicates that the first known cases of NB.1.8.1 were registered at the end of April, although it first appeared in samples earlier in the year. Common symptoms align with typical Omicron subvariants, including fatigue, fever, and muscle aches. A distinctive symptom, a severe sore throat known as “razor blade” throat, causing sharp stabbing pain when swallowing, has also been reported.

The "Nimbus" variant appears to be more transmissible than previous strains, with notable increases reported in India, Hong Kong, Singapore, and Thailand. Current COVID vaccines are expected to remain effective against this variant, protecting against severe illness.