CLEVELAND (WJW/NEXSTAR) — Recently added to the World Health Organization’s list of coronavirus variants of interest, the B.1.621, or mu variant, has been detected in 49 states.

That’s according to a report from FOX News, which cites estimates compiled by

Nebraska is reportedly the only state where the mu — or B.1.621 — variant has not yet been detected.

The mu variant was first identified in Colombia in January 2021 but wasn’t officially labeled as a variant of interest (VOI) until Aug. 30, according to the Weekly Epidemiological Update published last week.

“The mu variant has a constellation of mutations that indicate potential properties of immune escape,” the organization wrote, noting that vaccinated individuals appear to show a “reduction in neutralization capacity” against mu.

As of last week, WHO indicated there were only “some” reports of larger outbreaks of mu, specifically in South America and Europe, along with “a few sporadic reports of cases.”

In total, WHO says the variant has been reported in 39 countries. 

WHO said further studies are needed to determine the characteristics of the mu variant. Other VOI being monitored by WHO include eta, iota, kappa, and lambda.

The organization has also listed several variants of concern, or VOC, which include the alpha, beta, gamma, and delta variants. These variants are similar in that they meet the criteria for a VOI, but are associated with either an increase in virulence, a decrease in the effectiveness of public health measures, or a “detrimental change in COVID-19 epidemiology,” among other possible factors.