U.S. daily The Hill says the World Health Organization(WHO) is keeping a close eye on a new COVID-19 variant called NB.1.8.1, or "Nimbus," as it is spreading rapidly in Europe, the Americas and the Western Pacific.

The paper quoted the U.S.’ Centers for Disease Control and Prevention (CDC) as saying on Wednesday that 37 percent of COVID-19 cases in the U.S. reported in the two weeks leading up to June 7 originated from the mutated omicron strain, while 38 percent were a result from an infection of the LP.8.1 strain, another omicron descendant. 

At the end of May, the CDC estimated the Nimbus variant caused about 15 percent of all COVID-19 cases while the LP.8.1 strain caused 57 percent of cases. 

The agency was quick to add, however, on its website "that due to low numbers of virus sequences being reported, precision in the most recent reporting period is low."

Currently, the WHO has designated six COVID-19 variants, including Nimbus, as "Variant Under Monitoring."