Rising Concerns Over Fast-Spreading New COVID Variant NB.1.8.1 (Nimbus)
A new version of the Omicron COVID-19 virus, known as NB.1.8.1 and unofficially nicknamed “Nimbus,” is spreading quickly around the world.
This has caused concern among health experts, who are now increasing their surveillance and reminding the public to continue following safety measures.
NB.1.8.1 was first identified in January 2025. Since then, it has spread rapidly across Asia, especially in China and Hong Kong, where it has become the most common strain.
Recently, it has also started appearing more frequently in Europe and North America, including multiple U.S. states.
The World Health Organization (WHO) reported that global COVID-19 activity has been rising since mid-February 2025.
The number of positive test results worldwide has reached 11 per cent, a figure not seen since July 2024.
According to data collected from various surveillance centers, as of May 11, 2025, 73 countries, regions, and territories had recorded an 11 per cent positivity rate.
This matches the peak seen in July 2024, when 99 countries reported a 12 per cent positivity rate. Back in mid-February 2025, this rate was just 2 per cent across 110 countries, showing a significant increase in only a few months.
Because of its rapid growth, NB.1.8.1 was officially classified as a “Variant Under Monitoring” (VUM) by the WHO on May 23, 2025.
This means that WHO’s Technical Advisory Group on Virus Evolution (TAG-VE) is watching it closely to better understand its behavior and impact.
Initial scientific studies show that the NB.1.8.1 variant has a strong ability to attach to human cells and spread easily, which may explain how quickly it is moving through populations.
While there are some signs that it may slightly reduce the effectiveness of existing antibodies, there is currently no evidence suggesting that it leads to more serious illness, increased hospitalisations, or different symptoms compared to other Omicron subvariants.
So far, the common symptoms remain similar and include tiredness, fever, sore throat, nasal congestion, mild coughing, and sometimes stomach problems.
In certain cases, patients have experienced a condition called persistent low-grade hyperthermia — a continuous elevation in body temperature caused by problems with the body’s temperature regulation system. This differs from the usual fever people get during an infection.
Although the virus is spreading in some parts of the world, many countries in Africa, Europe, and the Americas are currently reporting low levels of COVID-19 activity.
In these areas, the positivity rate ranges between two and three per cent, which is still relatively low.
In Kenya, the Ministry of Health has not yet released any public statement about the new variant, likely because infection rates remain low.
However, global health organizations have warned that the emergence of new variants is normal in the evolution of viruses and should not cause panic.
At the same time, they have stressed the importance of staying alert and continuing health precautions.
Health experts are encouraging people to stay up to date with their COVID-19 vaccinations, especially older adults aged 65 and above and people with underlying health conditions.
They also emphasized the need for ongoing genetic monitoring of the virus, prompt sharing of data among countries, and strong plans for pandemic response to track how NB.1.8.1 is changing and spreading.
Additionally, people are advised to continue following simple protective habits like regular handwashing and proper hygiene. The use of approved antiviral treatments also remains important in helping manage infections.
Since the COVID-19 pandemic began in early 2020, Kenya has officially recorded around 5,689 deaths related to the virus. Globally, the number of confirmed COVID-19 deaths is estimated to be between 7.01 million and 7.05 million.
However, the WHO and many researchers believe that the true number of deaths caused directly or indirectly by COVID-19 is much higher.
These so-called “excess deaths” — which include people who died due to healthcare system disruptions — are estimated to range between 14.9 million and over 30 million for the years 2020 and 2021 alone.
In conclusion, although NB.1.8.1 is spreading rapidly and deserves careful observation, it is not currently seen as a cause for major alarm.
Health authorities continue to remind the public that regular updates to vaccines, strong monitoring, and basic hygiene practices remain key tools in managing the ongoing threat of COVID-19.
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