Mu, also known by scientists as B.1.621, was added to the WHO’s list of variants “of interest” on Aug. 30, the international health organization said in its weekly Covid epidemiological report published late Tuesday.

The variant contains genetic mutations that indicate natural immunity, current vaccines or monoclonal antibody treatments may not work as well against it as they do against the original ancestral virus, the WHO said.

 The mu strain needs further study to confirm whether it will prove to be more contagious, more deadly or more resistant to current vaccines and treatments.

Mu “has a constellation of mutations that indicate potential properties of immune escape,” the WHO wrote in its report Tuesday.

“Preliminary data presented to the Virus Evolution Working Group show a reduction in neutralization capacity of convalescent and vaccine sera similar to that seen for the Beta variant, but this needs to be confirmed by further studies,” it added.

The new variant, mu, was first identified in Colombia but has since been confirmed in at least 39 countries, according to the WHO. Although the global prevalence of the variant among sequenced cases has declined and is currently below 0.1%, its prevalence in Colombia and Ecuador has consistently increased, the agency warned.