The WHO says it is monitoring a new variant of Covid called “mu”


The World Health Organization is monitoring a new variant of coronavirus called “mu” that the agency says has mutations that have the potential to bypass the immunity provided by a previous Covid-19 infection or vaccination.

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

The variant contains genetic mutations that indicate natural immunity, current vaccines or monoclonal antibody treatments may not work as well as against the original ancestral virus, the WHO said. The mu strain needs further research to confirm whether it will prove more contagious, more deadly, or more resistant to current vaccines and treatments.

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

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

The agency is monitoring four “worrying” variants, including Delta, which was first discovered in India and is currently the most widespread variant in the US; Alpha, first discovered in the UK; Beta, which was first detected in South Africa, and Gamma, which was first detected in Brazil. A variant of concern is generally defined as a mutated strain that is either more contagious, more lethal, or more resistant to current vaccines and treatments.

It also observes four other interesting variants – including lambda, which was first identified in Peru – that have caused outbreaks in several countries and that have genetic alterations that could make them more dangerous than other strains.

Delta was an interesting variant until the WHO reclassified it in early May after preliminary studies found it could spread more easily than other versions of the virus. This variant has since been blamed for a number of major outbreaks around the world, including in the United States.

The new variant, mu, was first identified in Colombia, but has now 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 risen steadily, the agency warned.

WHO said more studies are needed to understand the clinical features of the new variant.

“The epidemiology of the mu variant in South America, particularly the joint spread of the delta variant, is being monitored for changes,” the agency said.