A new subvariant of the Omicron SARS-CoV-2 virus, identified as NB.1.8.1 (unofficially nicknamed Nimbus), is rapidly gaining ground globally, prompting intensified monitoring and calls for sustained public health measures from leading international health institutions.
First detected in January 2025, NB.1.8.1 has quickly spread across Asia, becoming the dominant strain in regions like China and Hong Kong, and was recently detected with increasing frequency in Europe and North America, including several states in the United States.
According to the World Health Organisation (WHO), since mid-February 2025, as per data available from sentinel sites, global SARS-CoV-2 activity has been increasing, with the test positivity rate reaching 11 per cent, levels that have not been observed since July 2024.
WHO further detailed that as of May 11 this year, the test positivity rate was 11 per cent across 73 reporting countries, areas, and territories. This level matched the peak observed in July 2024 (12 per cent from 99 countries) and marks a rise from two per cent reported by 110 countries back in mid-February 2025.
The new variant was designated as a Variant Under Monitoring (VUM). This classification, issued on May 23, 2025, signified that the WHO's Technical Advisory Group on Virus Evolution (TAG-VE) was closely tracking its prevalence and characteristics due to its rapid growth.
Preliminary data from virological studies suggest that NB.1.8.1 exhibits strong binding affinity to human cells and high infectivity, which may explain its rapid spread.
Even so, while there is evidence of a slight reduction in antibody effectiveness compared to previous variants, current findings do not indicate that NB.1.8.1 causes more severe illness, hospitalisations, or different symptoms than other currently circulating Omicron descendant lineages.
Common symptoms include fatigue, fever, sore throat, congestion, mild cough, and occasional gastrointestinal issues. Reportedly, in some cases, individuals have experienced persistent low-grade hyperthermia, a condition where the body temperature is elevated beyond normal due to failed thermoregulation, differing from typical fever.
Statistics revealed that countries in the African region, European region, and the Americas are currently reporting low levels of SARS-CoV-2 activity, with the rate ranging from two to three per cent.
Currently, the Ministry of Health has not issued any formal communication on the matter, supposedly due to the low rate of infection.
Despite the alarm that such information might cause, global health agencies stressed the need for vigilance, noting that the emergence of new variants is an expected part of viral evolution and does not signal a public health emergency.
In addition, they have urged individuals to be up to date with their vaccinations, especially those aged 65 and older and individuals with underlying health conditions. Authorities also stressed the importance of ongoing genomic surveillance, timely data sharing, and robust pandemic preparedness to track the variant's evolution and impact.
This was in addition to adhering to basic protective measures such as maintaining good hygiene and using existing antiviral treatments.
The COVID-19 pandemic, which emerged in early 2020, claimed around 5,689 casualties in Kenya according to the most recent data. Globally, the number of confirmed COVID-19 deaths reported was around 7.01 million to 7.05 million.
However, it is widely acknowledged by organisations like the WHO and other researchers that the actual number of deaths directly or indirectly associated with COVID-19 (known as "excess deaths") is significantly higher, with estimates ranging from 14.9 million to over 30 million for 2020 and 2021 alone.
