Over five years after the initial outbreak, COVID-19 continues to dominate headlines worldwide, fueled by the emergence of a new variant detected across multiple countries, including the UK. This resurgence underscores the persistent challenge posed by the virus, even as global vaccination efforts have progressed.
The latest strain, designated NB.1.8.1, now accounts for approximately 11% of all reported COVID-19 cases globally. Recent reports confirm its presence in regions such as Northern Ireland and Wales, signaling its expanding reach within the UK. While current evidence suggests that NB.1.8.1 does not cause more severe illness, experts believe it may infect human cells more efficiently and could lead to symptoms affecting the gastrointestinal system, such as diarrhea, constipation, and nausea.
Since its initial identification in January 2025, the NB.1.8.1 variant has rapidly spread to numerous countries, including the United States, Australia, Thailand, and has become the predominant strain in China and Hong Kong. This pattern highlights the ongoing global circulation and adaptation of the virus, emphasizing the importance of continuous monitoring and research.
Understanding the NB.1.8.1 Variant
The World Health Organization (WHO) classifies NB.1.8.1 as a “variant under monitoring,” representing roughly 10.7% of all genetic sequences submitted globally. This classification indicates that while it is not currently deemed a major threat, it warrants close observation due to its potential implications.
A WHO spokesperson explained: “SARS-CoV-2 continues to evolve, and between January and May 2025, we observed shifts in the dominant variants worldwide. Early in the year, the most prevalent variant was XEC, followed by KP.3.1.1. By February, the circulation of XEC declined, while LP.8.1 increased, becoming the most detected variant by mid-March. Since mid-April, the prevalence of LP.8.1 has slightly decreased, with NB.1.8.1 increasingly being identified.”
Data from GISAID, a global repository of viral genetic sequences, indicates that the majority of confirmed NB.1.8.1 cases were recorded in early April, suggesting a recent surge in its detection. Countries such as the United States, China, Thailand, and Australia have all reported cases, reflecting its widespread distribution.
Symptoms and Transmission of NB.1.8.1
Although preliminary data suggests that NB.1.8.1 may spread more readily than previous variants, there is no current evidence indicating it causes more severe illness. The WHO has noted that the severity profile remains similar to earlier Omicron subvariants.
Microbiologist and immunologist Professor Subhash Verma from the University of Nevada, Reno, explained to CBS News: “Current data indicates that NB.1.8.1 does not lead to increased severity compared to older variants, but its higher transmissibility means it can spread more easily without necessarily causing worse health outcomes.” In essence, it appears to be more contagious.
Typical symptoms associated with this variant mirror those of other Omicron subvariants, including fatigue, fever, muscle aches, and sore throat. Despite the detection of cases in Northern Ireland, Wales, and popular tourist destinations abroad, the decline in testing rates makes it increasingly challenging to accurately gauge the true number of infections.
Effectiveness of COVID-19 Vaccines Against NB.1.8.1
Current COVID-19 vaccines are expected to remain effective against NB.1.8.1, providing significant protection against severe disease and hospitalization. Ongoing research continues to monitor vaccine efficacy as the virus evolves, but existing immunizations remain a critical tool in managing the pandemic.
