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. President William Ruto receiving a Covid-19 Vaccine (alleged to be Russian Sputnik V) jab at his residence in Karen, Nairobi on Tuesday, March 30, 2021.
